1
general::
Recover quickly, as in She had pneumonia, but she bounced back in less than a week. This expression is a metaphor for the rebound of a ball or some elastic material.
American Heritage Idioms
2
general::
Phrase(s): bounce back (from something)
1. Lit. [for something] to rebound; [for something] to return bouncing from where it had been. • The ball bounced back from the wall. • A rubber ball always bounces back. 2. and bounce back (after something) Fig. [for someone] to recover after a disability, illness, blow, or defeat. (See also rebound from something.) • She bounced back from her illness quickly. • She bounced back quickly after her illness.
McGrawhill's American Idioms And Phrasal Verbs