To call a junior sailor over to where your standing or sitting with the intent of jacking him/her up (yelling at him/her) for a minor offense. The person shipmating must use a "come here" motion with their hand by opening and closing it in rapid succession. Shipmating is normally done only by senior enlisted (Chief Petty Officer) sailors.
One can "shipmate" multiple people/things at a time by holding up both arms and possibly a leg.
The shipmate may actually be anyone or anything. Drunk Chief's have been known to shipmate signs, coffee cups, beer bottles, or prostitutes.
Background: In the U.S. Navy the term "shipmate" is seen as mostly derogatory in nature. Normally one is only called shipmate when they are in trouble or have done something wrong. The term shipmating was coined to describe the act when a Chief jacks up a sailor by calling him shipmate and motioning for him to present himself by the "come here" motion with his hand.
That Chief just shipmated those sailors for shopping in their work uniform. He's really getting his shipmating down, I watched him jack up 20 sailors today.
"Hey, do you guys want to go shipmating today?" "We can jack some dudes up down at the Navy Exchange (department store)".