British Dictionary definitions for unstably
- (of an elementary particle) having a very short lifetime
- spontaneously decomposing by nuclear decay; radioactivean unstable nuclide
Word Origin and History for unstably
early 13c., "apt to move," from un- (1) "not" + stable (adj.). Cf. Middle High German unstabel. Meaning "liable to fall" is recorded from c.1300; sense of "fickle" is attested from late 13c. An Old English word for this was feallendlic, which might have become *fally.