laxity
Concise Oxford English Dictionary © 2008 Oxford University Press:
lax/laks/
▶adjective
- 1 not sufficiently strict, severe, or careful.
- 2 (of the limbs or muscles) relaxed.
- 3 Phonetics (of a speech sound, especially a vowel) pronounced with the vocal muscles relaxed. The opposite of tense1.
– derivatives
laxity noun,
laxly adverb,
laxness noun.
laxity noun,
laxly adverb,
laxness noun.
– origin ME: from L. laxus.
'laxity' also found in these Oxford entries:

