(physics) The broadening of the spectral lines of a high-temperature or rapidly-rotating object due to redshifting of spectral lines from atoms and molecules moving away from the observer and blueshifting of spectral lines from atoms and molecules moving toward the observer.

(idiomatic) To increase someone's interests, skills, or experiences beyond their current range.

(archaic) third-person singular simple present indicative form of broaden

(archaic) second-person singular simple present form of broaden