When a man and woman are ass-to-ass (while on their backs) and they decide to put 1/2 of a string of anal beads in each others ass so that neither can leave. Then the male jerks off and just before he shoots his load in his partner's face he yells, "engage!" like Captain Jean-Luc Picard. Can also be done by a senior male on his female partner using his really saggy balls instead of anal beads.
Mike "Oh man, I had Jennifer over last night and gave her a Captain's Anchor!"
James "How was it?"
Mike "She was pretty pissed, and my ass is really sore today."