What it means
Not fussed means you genuinely do not mind either way, no strong preference, take it or leave it. It is the mild, easygoing British shrug you give when someone asks where to eat or what to watch and you really could go either way.
Usage examples
"You can have the last slice, I'm not fussed."
"Pizza or curry? Honestly not fussed, you pick."
Where it comes from
From "fuss", the bother and bustle of caring a great deal about something. To be not fussed is to have none of that fuss in you over the matter, calmly indifferent rather than plain lazy.
Other ways to say it
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