To be homosexual.
From cricket or baseball, in print c. 1990.
bat an eyelid
To react in any slight way; to respond; to care.
bat a thousand
To achieve success at each attempt.
bat five hundred
To be successful half of the time; to have a success rate of 50%.
bat one's eyes
To signal or feign by fluttering one's eyelids, as romantic interest.
bat the breeze
To chat; to shoot the breeze.