off one's own bat
At one's own instigation, of one's own accord.
My boss didn't tell me to reorganize the filing system; I did it off my own bat.
ADJ
baseball, cricket, table tennis
VERB + BAT
grip, hold | carry | swing
ADJ
fruit, pipistrelle, vampire
BAT + VERB
flutter, fly | roost | squeak
PHRASES
a species of bat
VERB + BAT
go in to
She went in to bat for her friend when everyone was criticizing him unfairly.
put sb in to
The home team won the coin flip and put the visitors in to bat first.
PREP
for
Our team needed someone to bat for us in the negotiation, and Sarah volunteered immediately.