When an extremelyanimated person speaks and emphasizes their words by moving their head rapidly from side to side. This movement is similar to the neck movements of geese when they walk.
geeking on that water is slang for saying that your drinking water that has had a molly or several dissolved into it. Molly is a pure form of MDMA gets you high as FUCK and the word geeking is a term for excitement .
this word is being defined in the song " drunk in love " by The Weeknd where he says " I've been popping, I've been rolling , since I was 17 I've been geeking on that water "