While rowing, "catching a crab" means to put one's oar in the water at the wrong time which results in the oar flipping parallel to the boat. When an oar goes from perpindicular (good) to parallel (bad) a rower must pull the oar in and over their head.

This can be difficult to fix as the boat moves.
Kate: I was rowing Port seat 6 yesterday when I totally caught a crab. It was horrible.
Ben: I remember! I was in 5 seat so I stopped to help you get your oar in order.
Kate: Thanks. It was intense. I hope I don't catch a crab at next Saturday's regatta!
by cannelle December 10, 2007
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When your pubic area is itchy and dirty after banging many people
Stink John was out catching crabs after he was banging the homeless lady on New Year's Day in Philadelphia
by Centimeter J June 11, 2019
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When someone is banging some dirty/slutty dude or chick.
Dude, I think Mike is catching crabs in the other room.

SMS: yo, stop ignoring me... what are you catching crabs right now????

Fuck it, I'm catching crabs tonight.

Cindy totally went catching crabs last night after she left the wedding.
by nicoleta paleta May 20, 2011
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