Readily availavble knowledge. As in "I don't know off hand."
An offhand remark is a remark that is spoken without thought. Similar to something blurted out.
Offhand; without previous study; extemporaneous; extempore; as, an impromptu verse., Something made or done offhand, at the moment, or without previous study; an extemporaneous composition, address, or remark., A piece composed or played at first thought; a composition in the style of an extempore piece.
Offhand is the odd term because it has nothing to do with unplanned actions.
That is not a phrase
If you mean towns and cities named Springfield, probably quite a few. I know three offhand - MA, IL, and OH.
what does the phrase rule of thumb mean
what does the phrase There`s ruin in store for you mean
a phrase that is traditional
"Grave" is a phrase that can mean serious.
"The phrase 'mean slow toffee' does not have a commonly recognized meaning. It may be a colloquial expression or a phrase that is not widely known."
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offhand