/ ˌɪməˈtjʊə(r); NAmE -ˈtʃʊr; -ˈtʊr/ adjective
1.
behaving in a way that is not sensible and is typical of people who are much younger :
immature behaviour
2.
not fully developed or grown :
immature plants
OPP mature
► im·ma·tur·ity / ˌɪməˈtjʊərəti; NAmE -ˈtʃʊr-; -ˈtʊr-/ noun [ U ]
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WORD ORIGIN
mid 16th cent. (in the sense premature , referring to death): from Latin immaturus untimely, unripe, from in- not + maturus ripe.