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1.
Someone who is experiencing the downsides of puberty. Total zits, voice cracks every second, and are usually 14-19. Can be seen with hats on backwards.
*in a hotel, where a gahoy is spotted in full swim gear*

Gahoy: Uhheeuheee where's the pool?

by Ilikecock123 March 09, 2009
 
2.
Acronym for:

Get
A
Hold
Of
Yourself

Should be used in substitution of the entire phrase, either in all caps as "GAHOY" or simply as an actual word "gahoy".
You're friend is going off the deep end on a wild tangent to your conversation and you tell him, "You need to gahoy."

You're friend is doing something in extreme, maybe eating an entire pizza, or obsessing about a girl. Tell him to "gahoy."

You're friend is drunk and OOC, crossing the line with his or her behavior. As a friend you need to step in and assert, "Gahoy!"
by Jed Wards March 18, 2011