Merriam-Webster Logo
SINCE 1828
Menu
×

An Encyclopædia Britannica Company

photonasty

noun pho·to·nas·ty
See What's Trending Now See More Trending Words

Definition of photonasty

plural -es
: a nastic movement that is associated with changes in light intensity

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!
Already a subscriber? Log in.

Origin and Etymology of photonasty

International Scientific Vocabulary phot- + -nasty; probably originally formed as German photonastie

Seen and Heard

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

show hide

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

raillery

play

good-natured ridicule

Get Word of the Day daily email!

TRENDING NOW

  1. embolization 'the process by which a blood vessel or organ is obstructed by a material mass'

  2. oleaginous 'marked by an offensively ingratiating manner or quality'

  3. pansexual 'sexual desire or attraction...not limited to a particular gender identity or sexual orientation'

  4. symbiote 'an organism living in symbiosis'

  5. charlatan 'faker or fraud'

SEE ALL

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Words at Play

image1481409085
9 Words from the Magical Realm

When language is magic

alt-5afefa13cc811
A Field Guide to British Noble Titles

Know your Duchess from your Baroness

image1720821498
7 Words for Bad Endings and Rough Situations

When it doesn't go as planned

alt-5afd9816817c1
Putting the History of 'Limelight' Center Stage

It's, ahem, an illuminating story.

Ask the Editors

video-ghost-words
Ghost Word

The story of an imaginary word that managed to sneak past our editors and enter the dictionary.

image1760257654
2017 Word of the Year: Behind the Scenes

How we chose 'feminism'

video-literally
Literally

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

video-his-or-her
Is Singular 'They' a Better Choice?

The awkward case of 'his or her'

Word Games

image1676440788
Words Used by Nabokov Quiz

How familiar are you with Nabokov’s unfamiliar vocabulary?

Take the quiz
cow-coming-home
Farm Idioms Quiz

Not your children's farm quiz.

Take the quiz
Spell It
Spell It

Can you spell these 10 commonly misspelled words?

Take the quiz
Word Winder's CrossWinder
Word Winder's CrossWinder

A game of winding words.

Play the game