little, slight (esp. AmE), small, soft (esp. AmE)
frightened (esp. AmE), pathetic

give, let out
The animal gave a pathetic little whimper.
She let out a whimper of pain.

hear

escape sb/sth
A small whimper escaped his lips.

quietly, softly
The dog whimpered softly.

slightly (esp. AmE)
pathetically

begin to, start to
hear sb

in
She was whimpering in fear.

with
The boy was whimpering with pain.

whimper like a child
He stirred in her arms, whimpering like a child.

Whimper is used with these nouns as the subject:
child