What does "crash course" mean?

A quick, intense course of learning, especially one which is informal or hurried.

Crash course

Common synonyms include: accelerated physics course, crash, crash program, crash programme, intensive, intensives.

noun

noun ·Rare ·Advanced level

Noun

1
A quick, intense course of learning, especially one which is informal or hurried. idiomatic
"He got a crash course in babysitting when his sister dropped off his nephew for the afternoon."
2
a rapid and intense course of training or research (usually undertaken in an emergency) wordnet

"He got a crash course in babysitting when his sister dropped off his nephew for the afternoon."