purr

verb
  1. to make a low continuous vibrating sound expressing contentment
  2. Usage: typically used for cats
  3. to speak in a soft, low voice expressing pleasure or satisfaction
  4. to run smoothly and quietly
  5. Usage: used for engines or machines
noun
  1. a low continuous vibrating sound made by a cat
  2. a similar low continuous sound made by an engine or machine

Examples