形容詞 offhand:

1. with little or no preparation or forethought
   同義詞：ad-lib, extemporaneous, extemporary, extempore, impromptu, offhanded, off-the-cuff, unrehearsed
2. casually thoughtless or inconsiderate
   同義詞：offhanded

副詞 offhand:

1. without previous thought or preparation
   同義詞：offhanded, offhandedly
2. in a casually inconsiderate manner
   同義詞：offhanded, offhandedly

1. He's a good salesman, but his offhand manner does tend to put people off.
   他是個很好的推銷員，可是他那隨便的態(tài)度容易使人產(chǎn)生反感。
2. I'm talking offhand, simply speaking my mind.
   我這是信口開河，隨便談談腦子里想的東西。

off.hand

adv.（副詞）
Without preparation or forethought; extemporaneously.
未經(jīng)準備地：沒有準備或事先思考；即席地
adj.also （形容詞） 也作
offhanded
Performed or expressed without preparation or forethought.See Synonyms at extemporaneous
即席表演的：沒有準備或事先思考而表演或表達的參見 extemporaneous

【引伸】
off.hand.edly
adv.（副詞）
off.hand.edness
n.（名詞）