Found in the following dictionaries
SOWPODS (Collins Scrabble Words)
"Boi" Definition
noun
A male bottom (i.e. submissive partner), defined not by junior age, but by his obedient role, especially when that implies him being subject to spanking and/or other punishment by the dominant "top".
Source: Wiktionary
An alternate spelling of boy.
Source: Wiktionary
An ox.
Source: Wiktionary
Any head of cattle.
Source: Wiktionary