trembler

1. One who, or that which, trembles.

   one who quakes and trembles with (or as with) fear

2. Any of various New World passerine birds of the genus Cinclocerthia.

3. The vibrating hammer, or spring contact piece of a hammer break, as of the electric ignition apparatus for an internal combustion engine.

4. A kind of security alarm triggered by vibrations or shock waves.

regular