iridium

UK: /aɪˈrɪdɪəm/ US: /ɪˈrɪdiəm/ ,(i rid′ē əm, ī rid′-)

WordReference Random House Learner's Dictionary of American English © 2025

i•rid•i•um /ɪˈrɪdiəm/   n. [uncountable]

1. Chemistry a precious metal resembling platinum.

WordReference Random House Unabridged Dictionary of American English © 2025

i•rid•i•um  (i rid′ē əm, ī rid′-), n. [Chem.]

1. Chemistry a precious metallic element resembling platinum: used in platinum alloys and for the points of gold pens. Symbol: Ir;
   at. wt.: 192.2;
   at. no.: 77;
   sp. gr.: 22.4 at 20°C.

• Latin īrid-, stem of īris rainbow (see iris) + -ium; so named from its iridescence when dissolved in hydrochloric acid
• 1804

Collins Concise English Dictionary © HarperCollins Publishers::

iridium / aɪˈrɪdɪəm ɪˈrɪd-/ noun

1. a very hard inert yellowish-white transition element that is the most corrosion-resistant metal known. It occurs in platinum ores and is used as an alloy with platinum. Symbol: Ir; atomic no: 77; atomic wt: 192.22; valency: 3 or 4; relative density: 22.42; melting pt: 2447°C; boiling pt: 4428°C

Etymology: 19th Century: New Latin, from irido- + -ium; from its colourful appearance when dissolving in certain acids