Answer: purring

AnswerCrossword Clue
PURRINGWell content
PURRINGLike a contented cat
PURRINGAudibly satisfied, as a kitten
purring(of a vehicle or engine) Move smoothly while making such a sound
purringSpeak in a low soft voice, esp. when expressing contentment or acting seductively
purring(of a vehicle or machine) Make such a sound when running smoothly at low speed
purring(of a cat) Make a low continuous vibratory sound usually expressing contentment
purringthe sound of a contented cat