noun: Initialism of institutional review board, a committee that reviews the designs of proposed experiments to confirm whether all the methods proposed are ethical.
noun: Initialism of investment review board, a committee of business executives who review investment choices, comparing against strategy and opportunity costs.
noun: Initialism of internal review board, an internal affairs division of a police department.
adjective: (finance) Initialism of internal ratings-based approach
noun: (historical) Initialism of Irish Republican Brotherhood, a secret organisation dedicated to the establishment of an "independent democratic republic" in Ireland between 1858 and 1924.
noun: (rugby, historical) Initialism of International Rugby Board, the name used by World Rugby, the worldwide governing body for rugby union, from 1998 to 2014.