Related Clues:
- Cat or engine sounds
- Purrs like an engine
- Sings without lyrics
- Hums like a tuned engine
- Good vibrations?
- Makes like a happy tabby
- Purrs, as an engine
- Audible responses to catnip
- Sings without singing
- Goes "mmm mmm mmm mmm," maybe
- Plays the kazoo, say
- Beehive sounds
- Sings to oneself
- Sounds from kittens or rabbits
- Whirs