An unusual or exceptional person or thing. / Used other than figuratively or idiomatically: see rare, bird.

(inorganic chemistry) The oxyanion IO₄⁻ or any salt containing this anion

(clocks, mechanics) The contrivance in a timepiece (winding wristwatch) which connects the train of wheel work with the pendulum or balance, giving to the latter the impulse by which it is kept in ...

plural of outburster