depressor

Short definition from Wiktionary

Noun

1. 1
   Anything that depresses: Any of several muscles whose contraction pulls down a part of the body.
2. 2
   Anything that depresses: A nerve or nerve fiber that decreases the activity or the tone of the organ or the part it innervates, such as lowering the blood pressure.
3. 3
   Anything that depresses: An instrument used to push something out of the way during an examination.