What exactly is cutting when lifting?

I don't know what "cutting" is, but you look pretty good in your profile pic. Good job!

I am doing stonglifts 5x5 and was curious what is "cutting"?

It means eating at a deficit. Many weightlifting do cycles of bulking (eating at a surplus to build muscle), and cutting to lose any fat they may have gained while bulking, or had to begin with.

There will come a point in a high volume program like SL when you will stall because it sounds like you are eating at a deficit right now. Your body will be unable to generate new muscle at the rate needed to support the ever-increasing weight on the bar. At that point you will probably need to decide to either ramp back off of SL and go towards something better-suited to your dietary intake, or go into a small bulk cycle. Most people who have gotten their aesthetics where they want them to be will cut until very lean, then bulk until they can't tolerate how soft they look, and commence to cutting back to what they prefer to look like. In order to get stronger, you will eventually need to be willing to gain weight, but it will ideally be LBM rather than fat (mostly).

bump as I have been bulking and gaining what I feel is just fat. So time to cut!

It's just dieting - i.e. eating at a deficit

I'm going to try to answer this to the best of my ability.

The term cutting is a bodybuilding term derived from the idea of shedding the layers of body fat covering your muscles by means of cardio and eating at a calorie deficit to reveal a more defined (ie "cut") physique.

Cutting is usually the phase in a bodybuilders fitness routine following a bulking phase wherein large amounts of mass, both muscle and fat, are purposely gained in a short period of time. Usually the point of the bulking phase is to surpass your weight goal a bit (sometimes as much as 20 lbs) so that when you do finally get to the cutting phase the muscles you reveal will be larger than they otherwise would be. Some bodybuilders accomplish this by eating massive amounts of food and doing zero cardio. Hopefully you're doing weightlifting during the process to minimize fat gains but nevertheless some of the weight gain will be fat which means less muscle definition hence the need for a cutting phase.

Once you've reached your bulking weight goal, next comes the cutting phase. This is where you start trimming the fat that was gained to reveal all the new muscle you built during the bulking phase. This is achieved by simply eating a deficit of calories and doing cardio (and hopefully still lifting) just like one would normally do to lose weight until you eventually get down to your final goal weight.

The idea behind the bulking and cutting technique is that your body is usually really good at building muscle when you're gaining weight and really good at burning fat when you're losing weight but it can be very difficult to both build muscle and lose fat at the same time. By focusing on only one at a time your body is able to get better results in a shorter amount of time.

Now from what I can tell by your picture you already look like you're in great shape and seem to be at a healthy weight so I'm not sure that cutting is right for you. I don't know what your fitness goals are but bulking and cutting is usually only used by bodybuilders trying to build bigger muscles. I would say whatever you're doing right now seems to be working out for you so I don't see a need to change anything.

I'm going to try to answer this to the best of my ability.

The term cutting is a bodybuilding term derived from the idea of shedding the layers of body fat covering your muscles by means of cardio and eating at a calorie deficit to reveal a more defined (ie "cut") physique.

You don't need to do any cardio while cutting if you don't want to. It's all about diet and losing body fat.

Of course you don't need to do cardio, but of all the things you could have nitpicked about in my post you chose to go with cardio? Sure you can starve yourself to lose weight but why not do cardio to help the process along? Your body will thank you if you do.

I'm going to try to answer this to the best of my ability.

The term cutting is a bodybuilding term derived from the idea of shedding the layers of body fat covering your muscles by means of cardio and eating at a calorie deficit to reveal a more defined (ie "cut") physique.

You don't need to do any cardio while cutting if you don't want to. It's all about diet and losing body fat.

Of course you don't need to do cardio, but of all the things you could have nitpicked about in my post you chose to go with cardio? Sure you can starve yourself to lose weight but why not do cardio to help the process along? Your body will thank you if you do.

Wow.

All I can do is laugh at this.

Nitpicked? You think I am anti-cardio?

Just pointing out that you don't NEED it as you implied.

You think I STARVE myself eating a minimum of 1650 calories which is 300 above my BMR and I tend to actually consume closer to 2000?

I love it when people on the interwebz get all offended and then start assuming things about others. All I intended to do was answer the OP with the plain and simple fact that cutting involves a calorie deficit, and by definition, no cardio is needed.