SINCE 1828

An Encyclopædia Britannica Company

Medical Dictionary

equilenin

play

noun equi·len·in \ ˌek-wə-ˈlen-ən , ə-ˈkwil-ə-nən \

medical Definition of equilenin

:a weakly estrogenic steroid hormone C₁₈H₁₈O₂ obtained from the urine of pregnant mares

Seen and Heard

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

show

WORD OF THE DAY

broadside

play

a strongly worded attack

Words at Play

alt-59cabc6d7aa91

How 'Premises' Came to Mean 'Property'

It goes back to the beginning

10 Uncommon Words for 'Drunkard'

Tosspots, stewbums, and all the rest

alt-59c94ad823f29

'Meat Sweats': The Cookout's Worst Nightmare

They're real, but is meat the cause?

alt-59c919f342079

'Diffuse' vs. 'Defuse'

Let us defuse the situation.

Ask the Editors

video-title-words-of-the-year-1066

Words of the Year: 1066

Or, Why Pig Meat is Called 'Pork' and Cow Meat is Called 'Beef'

How Often Is 'Biweekly'?

Don't get us started on 'bimonthly'

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless

Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals

Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

young-plant-shoots

Merriam-Webster's New Words Quiz—Fall 2017 Edition!

You're going to have to memorize the dictionary again.

Take the quiz

stylized-drawing-of-woman-pole-vaulting-across-gap-to-get-trophy

Challenging Vocabulary Quiz Returns!

No tricks, just difficult words.

Take the quiz

True or False?

Test your knowledge - and maybe learn something along the way.

Take the quiz

Bee Cubed

Listen to the words and spell through all three levels.

Play the game