SINCE 1828

An Encyclopædia Britannica Company

Psilotaceae

plural noun Psi·lo·ta·ce·ae \ ˌsīlōˈtāsēˌē \

Definition of Psilotaceae

:a family of plants that are usually placed in order Psilotales and are characterized by nearly naked stems, minute scalelike leaves, and 2- or 3-celled sporangia — compare psilotum , tmesipteris

—

psilotaceous

adjective

There's more!

Love words? You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

More than 250,000 words that aren't in our free dictionary
Expanded definitions, etymologies, and usage notes
Advanced search features
Ad free!

Origin and Etymology of psilotaceae

New Latin, from Psilotum, type genus + -aceae

Seen and Heard

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

show

WORD OF THE DAY

shofar

play

a ram's-horn trumpet used in Judaism

Words at Play

alt-59c2960017c94

The Ambiguity of Pushing 'Up' and 'Back'

When you push a meeting, where does it go?

Silent Letters

When each letter can be seen but not heard

alt-59c17b8172892

'So Long': A Common But Mysterious Goodbye

Its origins are surprisingly murky.

alt-59c13729150dc

"Immune to" or "Immune from"?

Nobody is immune to this question.

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

Spell It

Can you spell these 10 commonly misspelled words?

Take the quiz

SCRABBLE® Sprint

SCRABBLE® Sprint

SCRABBLE® fans, sharpen your skills!

Play the game