go down

1.  Descend to a lower level; drop below the horizon, fall to the ground, or sink. For example, Don't let the baby go down the stairs alone, or The sun went down behind the hill, or I was afraid the plane would go down, or The ship went down and all hands were lost. [c. 1300]
2.  Experience defeat or ruin, as in They went down fighting, or The boxer went down in the first round. [Late 1500s]
3.  Decrease, subside, as in After Christmas prices will go down, or As soon as the swelling goes down it won't hurt as much. [Second half of 1600s]
4.  Be swallowed, as in This huge pill just won't go down, or Your wine goes down very smoothly. [Second half of 1500s]
5.  Be accepted or believed, as in How did your speech at the convention go down? When it takes an object, it is put as go down with, as in It's hardly the truth but it still goes down with many voters. [c. 1600]
6.  Also, go down in history. Be recorded or remembered, as in This event must go down in her book as one of the highlights of the year, or This debate will go down in history. [Late 1800s]
7.  Occur, take place, as in Really crazy behavior was going down in the sixties. [Slang; mid-1900s] Also see come down, def. 4.
8.  Be sent to prison, as in He went down for a five-year term. [Slang; c. 1900]
9.  In the game of bridge, fail to fulfill one's contract (that is, take fewer than the required number of tricks), as in We had bid four hearts and the bad distribution made us go down. [Early 1900s] Also see the subsequent idioms beginning with go down.

Definition: lose, fall
Antonyms: gain, go up, increase

The verb has 8 meanings:

Meaning #1: move downward and lower, but not necessarily all the way
  Synonyms: descend, fall, come down

Meaning #2: go under, "The raft sank and its occupants drowned"
  Synonyms: sink, settle, go under

Meaning #3: grow smaller
  Synonyms: decline, wane

Meaning #4: be recorded or remembered

Meaning #5: be ingested

Meaning #6: be defeated

Meaning #7: disappear beyond the horizon; of celestial bodies such as the sun and the moon
  Synonyms: set, go under

Meaning #8: stop operating
  Synonym: crash