1. an abbreviation of ireland.
2. assimilated form (in latin, etc.) of in- before r. in the following words, in the etymology, the prefix ir- is usually referred directly to the original in- or in.
3. assimilated form (in latin, etc.) of in- before r. in the following words, in the etymology, the prefix ir- is usually referred directly to the original in-.
4. an abbreviation of irish.
5. in chem., the symbol for iridium.

1. a board of the british government that administers and collects major direct taxes
2. a heavy brittle metallic element of the platinum group; used in alloys; occurs in natural alloys with platinum or osmium