Seriously, what does "toning up" mean??

HeidiMightyRawr

As much as I hate that phrase...
Lower body fat + some muscle definition = a toned look.

You may see skinny people with hardly any body fat, but it doesn't look very firm, and things sag or don't look like they have much shape - that's not very toned. If you create some muscle there, even a little, it will create more shape and definition making you look more firm and toned.
If your body fat is quite high, you need to lower it a little or you won't have much definition.

MaximalLife

Less Fat - More muscle!