1) Aggressive cat 2) Cat on the prowl 3) Cat that catches rodents 4) Cat that earns its keep 5) Cat that hunts rodents 6) Cat with chores 7) Cat worth its keep 8) Cat, often 9) Certain rodent catcher 10) Domestic cat 11) Domestic predator 12) Effective cat 13) Farm cat 14) Farm feline 15) Felis catus 1) Cat 
• (n.) A cat that catches mice. • (n.) One who pries about on the lookout for something.
Mous'er noun 1. A cat that catches mice. 2. One who pries about on the lookout for something. 
[n] - a cat proficient at mousing
noun a cat proficient at mousing
an animal that catches mice: Our cat is a good mouser. · a person or thing that seeks or prowls, as if for prey.