He has never given a rat's arse about anyone else's opinion.

I am giving a rat's arse about what he thinks.

The Tate's shrew rat is a small mammal found in Southeast Asia.

The New Guinean rat is a small rodent native to the island of New Guinea.

The blind mole rat is a fascinating creature.

The blind mole-rat is a fascinating creature.

Desert mole rats are fascinating creatures that live in underground burrows.

The desert mole rat is a fascinating creature that lives in arid regions.

I learned how to make rat-tail splices in my sailing class.

He ran up the stairs like a rat up a drainpipe.