Impromptu and Off-hand

Impromptu adjective - Made or done without previous thought or preparation.

Off-hand and impromptu are semantically related. In some cases you can use "Off-hand" instead an adjective "Impromptu". informal substitute

Off-hand adverb - Without preparation.

Impromptu and off-hand are semantically related. You can use "Impromptu" instead the phrase "Off-hand" as an adjective or an adverb. informal substitute