tranquilize

from The American Heritage® Dictionary of the English Language, 4th Edition

• transitive v. To make tranquil; pacify: "Nothing contributes so much to tranquilize the mind as a steady purpose” ( Mary Shelley).
• transitive v. To sedate or relieve of anxiety or tension by the administration of a drug.
• intransitive v. To become tranquil; relax.
• intransitive v. To have a calming or soothing effect.

from Wiktionary, Creative Commons Attribution/Share-Alike License

• v. To use a drug to sedate a person or animal.
• v. To make something or someone tranquil; to pacify or calm.
• v. To become tranquil; to relax.
• v. To calm down.

from the GNU version of the Collaborative International Dictionary of English

• transitive v. To render tranquil; to allay when agitated; to compose; to make calm and peaceful

from The Century Dictionary and Cyclopedia

• To render tranquil or quiet; allay when agitated; compose; make calm or peaceful.
• Synonyms To quiet, still, soothe, calm, lull, hush.
• To become tranquil; also, to exert a quieting or calming effect.
• Also spelled tranquilise, tranquillise.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• v. cause to be calm or quiet as by administering a sedative to
• v. make calm or still