Definition of "extensor" [ex•ten•sor]

• A muscle that extends or straightens a limb or body part. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Accordingly the so-called extensor muscles of the body need frequent action."
• "A projecting structure termed the extensor process (or extensor attachment) is present between the carpal trochlea and the alular digit; it belongs to metacarpal I (also called the alular metacarpal), but this is hard to appreciate in modern birds because metacarpal I is fused imperceptibly into the carpometacarpus as mentioned above [in the adjacent diagram, from"
• "What you can't see in this shot is that my feet are actually cut, and (for additional grossness) I can pump up my extensor digitorum brevis muscle so that it's ripped and the veins over it pop."