Etymology 1

• From the military term GIS, "general impression and shape"
• Possible contraction of just is (in the sense that a particular bird species "just is" that species).

Noun

1. The unique characteristics of a bird species that enable it to be immediately identified by an experienced birdwatcher who has seen that bird before and is familiar with its appearance and behaviour.

Verb

1. To ejaculate; to eject semen.
2. To ejaculate on, over, or into; to cover in semen.