1. One that serves to tranquilize, as soothing music.
2. Any of various drugs used to reduce tension or anxiety; an antianxiety agent.
3. Any of various drugs used to treat psychotic states; an antipsychotic drug. Not in scientific use.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.