sudden

Happening without warning; unforeseen.

Happening or done without delay; hasty or immediate.

Characterized by sharp change in elevation; precipitous.

(all of a sudden) Very quickly and unexpectedly; suddenly.

Suddenly; unexpectedly.

Happening without notice, instantly and unexpectedly; immediate; instant.

Found or hit upon unexpectedly.

Hastily made, put in use, employed, prepared, etc.; quick; rapid.

Hasty; violent; rash; precipitate; passionate.

In zoology, abrupt; sharply defined from neighboring parts: as, a sudden antennal club; a sudden truncation.