adj.
Having a soothing, calming, or tranquilizing effect; reducing or relieving anxiety, stress, irritability, or excitement.
n.
An agent or a drug having a soothing, calming, or tranquilizing effect.
[Middle English, from Old French sedatif, from Medieval Latin sēdātīvus, from Latin sēdātus, past participle of sēdāre, to calm. See sedate1.]
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.
