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1.
When a person at work clocks in ("punches in") their friend when their friend is late to work.
Did you you clock in for Stevie?

Oh yes.

Good old buddy punch!
by Stewart Larkin August 26, 2006
 
2.
Noun.
To punch a friend on the arm or shoulder during a greeting.
John: "Hey man, long time no see!"
*punch*
Henry: "Dude, that fricken hurt."
John: "Relax, it's just a buddy punch. Wuss."
by CheckersMcGavern October 21, 2008