look up any word, like thot:
 
1.
Start doing something. Get down to it.
We are ready to start, let's have at it.
by Hoda Man July 23, 2008
 
2.
Command to do something.
When placing a plate of brownies down infront of his drunk friends, Tom said "have at it boys".

After seeing Sean get punch repeatedly by the opposition in the middle of a maul in a rugby game, Tom grabbed the offender in a full-nelson and positioned him face-first to Sean, saying "have at it".
by Dirty Little Tommy August 03, 2005
 
3.
to have sex for the first time.
Tonight, the bride and groom are going to have at it.
by Hard cherry December 22, 2011