unperturbed

verb (used with object)

1. to disturb or disquiet greatly in mind; agitate.
2. to throw into great disorder; derange.
3. Astronomy. to cause perturbation in the orbit of (a celestial body).

adjective

1. not disturbed or troubledunperturbed by the prospect of a fight

verb (tr; often passive)

1. to disturb the composure of; trouble
2. to throw into disorder
3. physics astronomy to cause (a planet, electron, etc) to undergo a perturbation

adj.early 15c., from un- (1) “not” + past participle of perturb. v.late 14c., from Old French perturber “disturb, confuse” (14c.) and directly from Latin perturbare “to confuse, disorder, disturb,” especially of states of the mind, from per- “through” (see per) + turbare “disturb, confuse,” from turba “turmoil, crowd” (see turbid). Related: Perturbed; perturbing.