rictus

A gaping grimace.

The expanse of an open mouth or a bird’s beak.

The corner of the mouth or the fleshy area where the upper and lower mandibles of a bird meet.

In ornithology, the gape of the bill; the cleft between the upper and the lower mandible when the mouth is open.

In botany, the throat, as of a calyx, corolla, etc.; the opening between the lips of a ringent or personate flower.

The gape of the mouth, as of birds; — often resricted to the corners of the mouth.

A bird’s gaping mouth

Any open-mouthed expression

a gaping grimace