Join Us On

An Encyclopædia Britannica Company

Spanish Central

Browse Dictionary Browse Thesaurus

Get our free apps!iPhone•iPad•Android

Word of the Day

Blog: Words at Play

Dictionary

ACS

abbreviation

Definition of ACS

1

American Chemical Society

2

American College of Surgeons

ADVERTISEMENT

Medical Dictionary

ACS

abbreviation

Medical Definition of ACS

antireticular cytotoxic serum

Browse

Next Word in the Dictionary: act (noun)Previous Word in the Dictionary: acryloylAll Words Near: ACS

ADVERTISEMENT

Seen & Heard

What made you want to look up ACS? Please tell us where you read or heard it (including the quote, if possible).

View Seen & Heard Highlights from Around the Site

Test Your Vocabulary!

10 Charming Words for Nasty People

Put-downs with flair

When "Literally" isn't, well, literal

How to use a word that (literally) drives some people nuts.

Know what this is?

Test your vocab with our fun, fast game

Ailurophobia, and 9 other unusual fears

Join Us

Merriam-Webster
on Facebook

Merriam-Webster
on Twitter

Bookstore: Digital and Print

Merriam-Webster references for Mobile, Kindle, print, and more.

See All

Other Merriam-Webster Dictionaries

© Merriam-Webster, Incorporated