look up any word, like ratchet:
 
1.
If said in a cheerful, praising tone, it means "You're doing great, continue the good work!"

If said in a warning tone, it is a threat that means "Stop it right now, or reap the consequences!"

Praise: Wow, you've lost 35 pounds on that diet! Keep it up!

Warning: I have had all I can take of your whining! Do you want a spanking? Keep it up...!
by MistressApril September 06, 2008
 
2.
A game that involves keeping something up, with out touching it.
Oh you know Tamara, she is so good at KeepItUp.
by Mr.Pickleton April 13, 2009
 
3.
It means to keep your dick hard during sex.
My husband can't keep it up anymore.
by mister mystery October 14, 2012