The adjective has 2 meanings:
Meaning #1:
with little or no preparation or forethought
Synonyms: ad-lib, extemporaneous, extemporary, extempore, offhand, off-the-cuff, unrehearsed
Meaning #2:
casually thoughtless or inconsiderate
Synonym: offhand
The adverb offhanded has 2 meanings:
Meaning #1:
without previous thought or preparation
Synonyms: offhand, offhandedly
Meaning #2:
in a casually inconsiderate manner
Synonyms: offhand, offhandedly
