The characteristic of having one testicle whether it be because one has been squashed into the other, because one has been surgically removed, or because the man (and/or woman) was born without a secondball.
Anushka is uni-testicular because her balls where squashed together by a cock shot.
A sea horse with a large unicorn horn implanted on the top of their skull. This is a rare species but you kind find them quite easily due to their Large green aura that follows them everywhere they swim.
We should solve this big bang theory using the majestic Uni-Corse's horn.