1
: readily or continually undergoing chemical, physical, or biological change or breakdown : unstable
a labile mineral
2
: readily open to change
has so labile a face that some of her scenes … rock with emotion Manny Farber

Did you know?

Labile was borrowed into English from French and can be traced back (by way of Middle French labile, meaning "prone to err") to the Latin verb labi, meaning "to slip or fall." Indeed, the first sense of labile in English was "prone to slip, err, or lapse," but that use is now obsolete. Other labi descendants in English include collapse, elapse, and prolapse, as well as lapse itself.

Examples of labile in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The mob is aroused and labile; the lumpy cops have no control, over the situation or over themselves. James Parker, The Atlantic, 12 Oct. 2024 Then the therapist could spend several minutes establishing a safe rapport with the patient while waiting for the memory to enter a labile state during the reconsolidation-updating window. Bj Casey, Scientific American, 14 May 2024

Word History

Etymology

French, from Middle French, prone to err, from Late Latin labilis, from Latin labi to slip — more at sleep

First Known Use

1603, in the meaning defined at sense 1

Time Traveler
The first known use of labile was in 1603

Browse Nearby Words

Podcast

Cite this Entry

“Labile.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/labile. Accessed 23 Mar. 2025.

Medical Definition

: readily or frequently changing: as
a
: readily or continually undergoing chemical, physical, or biological change or breakdown
a labile antigen
b
: characterized by wide fluctuations (as in blood pressure or glucose tolerance)
labile hypertension
labile diabetes
c
: emotionally unstable

More from Merriam-Webster on labile

Love words? Need even more definitions?

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