noun
Pharmacology1A greyish-green powder consisting of a basic iodide and gallate of bismuth, used chiefly as a topical antiseptic, either in solid form or as an ointment.
Chemical name: bismuth 3,4,5-trihydroxybenzoate hydroxide iodide; BiC₇H₆IO₆.
2Tretinoin.
Origin
Late 19th century; earliest use found in The Lancet. From German Airol, apparently an arbitrary formation. Compare:2 apparently independently reintroduced for a different and unrelated substance.
Are You Learning English? Here Are Our Top English Tips