Impromptu and Stopgap

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

Stopgap and impromptu are semantically related In some cases you can use "Stopgap" instead an adjective "Impromptu".

Stopgap noun - A temporary replacement.

Impromptu and stopgap are semantically related in makeshift topic. You can use "Impromptu" instead an adjective "Stopgap", if it concerns topics such as temporary, temporarily helping.