Originally Posted by
Trakhak
And, as you must have noticed when you typed your reply, the Bike Forums spellchecker agrees with me in rejecting the neologism "groupset" but is perfectly happy with the four counter-examples you offered above.
Drawing any conclusion about the validity of a word based on its exclusion from a spell checker dictionary is misguided. Most spell checkers start out with a default dictionary that is supplemented with words that are appropriate (and possibly unique) for the subject. There is no deep meaning behind the absence of groupset from the BF dictionary -- it's missing only because no one has bothered to add it.