A small, round orange-like fruit that's rather sour. Can eat skin, though. Squeeze out seeds first.
Also can be used to call someone over to you.

Someone who takes christianity too seriously or someone who believes all sex is very very wrong.

A tasty little fruit that looks like a miniature orange. This yummy treat is the result of a horticultural experiment in which a dickweed was crossed with a pussywillow yielding the kumquat.

one wicked sweet fruit. although it's actually kind of bitter.

Substance released in the form of a bullet (in shape and size) as a person squats on top of his/her partner's face; may be fruity in flavour - depends on what materials have been consumed by the kumquatter earlier.

Alternatively, a fruit of the Chinese Orange kind.

a young individual who goes through life constantly disappointing people with his/her infinite failures

Used as an insult.