“Over 15”? Perhaps. I only count 14 definitions, though:
- To proceed, move, or change to a lower place or condition; to descend (from, †of); also transf. (of a road, passage, etc.) to lead downwards. Of a vessel: To go to the bottom, sink. to go down on one's knees (see knee n.).
- To extend, be continued down to a certain point.
- To be overthrown; to fall before a conqueror.
- To be set down in writing.
- Of waves, wind, etc.: To subside.
- To be swallowed. (Cf. down adv. 11.)
- fig. To find acceptance (with a person).
- To deteriorate; to decline in health or prosperity; to collapse or die. Also, to be subject to or suffer with (a specified illness or disease).
- To go away from a university or college; spec. to leave it permanently.
- To be sent to prison. slang.
- Bridge. To fail to fulfil one's contract.
- In a card-game: to put one's cards on the table; to reveal one's cards.
- To happen. slang (orig. U.S.).
- Usu. with on: to perform fellatio or cunnilingus on (a person). slang (orig. U.S.).
I suggest we’re talking about sense 10 here, possibly influenced by sense 3.
By the way, I can confirm that sense 11 is not limited to Bridge. It also occurs in card games like Euchre and Sheepshead. Basically any trick-taking card game where you don’t “make” whatever you are supposed to, which in Euchre is trick-count and in Sheepshead is point-count.
I still think this is General Reference.