Definition of thorax
1 : the part of the vertebrate body between the neck and the abdomen If you count the vertebrae in the necks and thoraxes of mice and chickens, you will find that a mouse has seven neck and 13 thoracic vertebrae, a chicken 14 and seven, respectively.— Matt Ridley also : thoracic cavity The thorax is evaluated for fluid at the flanks and for pneumothorax anteriorly. — Christoper L. Moore
2 : the middle of the three chief divisions of the body of an insect
Of nearly a million described species of insects, none has a biramous appendage, and nearly all have exactly three pairs of limbs on the thorax.— Stephen Jay Gould This haunting pitch issues from drum tissue stretched over the thorax of the male annual cicada …— Ted Williams also : the corresponding part of a crustacean or an arachnid The brown recluse spider … is brown and has fuzzy body hair and a dark violin- or pear-shaped band on the dorsum of its thorax. — Peter F. Weller
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Test Your Vocabulary
Slippery Words Quiz—Changing with the Times
- What is an earlier meaning of nice?

Test your visual vocabulary with our 10-question challenge!
TAKE THE QUIZ
A daily challenge for crossword fanatics.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridgedWords at Play
Ask the Editors
Word Games
Slippery Words Quiz—Changing with the Times
Do you know these earlier meanings of words?
Take the quizWords of Snow and Ice Quiz
A selection of words from the chillier parts of t...
Take the quizName That Thing
Test your visual vocabulary with our 10-question ...
Take the quizWord Winder's CrossWinder Play the game
Share thorax
Time Traveler for thorax
The first known use of thorax was in the 15th century
See more words from the same century