A three letter word for gender is sex.
There is no opposite gender for a neuter noun. The word paper is a neuter noun, a word for something that has no gender.
There is no specific gender variation for the word author.
The word drank does not have a gender
The 8-letter "opposite gender" of a male giant is "giantess." (There is no common 8-letter antonym to a giant or to the adjective giant.)
There is no opposite gender for the noun 'misdeed'. The noun misdeed is a neuter noun, a word with no gender.