Initialism of institutional review board, a committee that reviews the designs of proposed experiments to confirm whether all the methods proposed are ethical.

(finance) Initialism of internal ratings-based approach

(historical) Initialism of Irish Republican Brotherhood, a secret organisation dedicated to the establishment of an "independent democratic republic" in Ireland between 1858 and 1924.

plural of IRB

A strait between Saaremaa and Courland in Latvia, connecting the Baltic Sea and the Gulf of Riga.

(weaponry) Initialism of intermediate-range ballistic missile.

(uncommon) snow leopard (large feline mammal, Uncia uncia, native to mountain ranges of central Asia)

(pharmacology) An angiotensin II receptor antagonist used mainly for the treatment of hypertension.

Alternative form of Arbil

plural of IRBM