Does it mean that you aim to keep your weight at a constant (150lbs) no more no less.
Does it mean you allow yourself to a plus / minus amount of extra / less weight?
I myself go by the plus / minus idea. I know that warmer months I am waaaaay more active and lose around 10lbs but over winter when I am more in the gym lifting etc. I will gain that weight back. I dont stress nor worry about it.