n.
See mercury (sense 1).
adj.
Unpredictable; mercurial: "a quicksilver character, cool and willful at one moment, utterly fragile the next" (Sven Birkerts).
[Middle English, from Old English cwicseolfor, living silver (translation of Latin argentum vīvum) : cwic, cwicu, alive + seolfor, silver; see silver.]
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
