/ fɪkˈseɪʃn; NAmE / noun
1.
[ C ] fixation (with / on sb/sth) a very strong interest in sb/sth, that is not normal or natural :
a mother fixation
He's got this fixation with cleanliness.
2.
[ U ] ( technical ) the process of a gas becoming solid :
nitrogen fixation
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WORD ORIGIN
late Middle English (originally as an alchemical term denoting the process of reducing a volatile spirit or essence to a permanent bodily form): from medieval Latin fixatio(n-) , from fixare to fix, both from Latin fixus , past participle of figere fix, fasten.