形容詞 immature:

1. characteristic of a lack of maturity
2. lacking in development
   同義詞：unformed
3. (used of living things especially persons) in an early period of life or development or growth
   同義詞：young
4. not fully developed or mature; not ripe
   同義詞：green, unripe, unripened
5. not yet mature
6. (of birds) not yet having developed feathers
   同義詞：unfledged

1. He pretends he's been around but he's really very immature.
   他裝作老於世故，而實(shí)際上卻很不成熟。
2. Not ripe or matured; immature.
   不成熟的未熟或成熟的; 不成熟的
3. Inexperienced, immature, or untried.
   無(wú)經(jīng)驗(yàn)的、不成熟的或未經(jīng)試驗(yàn)的
4. Silly, immature behavior.
   愚蠢的，不成熟的行為

im.ma.ture

adj.（形容詞）
Not fully grown or developed.See Synonyms at young
未長(zhǎng)成的，未充分發(fā)展的：生長(zhǎng)或發(fā)展不完全的參見 young
Marked by or suggesting a lack of normal maturity:
不成熟的：以缺乏正常的成熟為標(biāo)志的：
例句：
silly, immature behavior.
愚蠢的，不成熟的行為

來(lái)源：
Latin imm3tôrus
拉丁語(yǔ) imm3tôrus
in- [not] * see in-
in- [不] *參見 in-
m3tôrus [mature] * see m3-
m3tôrus [成熟的] *參見 m3-

【引伸】
im.mature.ly
adv.（副詞）
im.matur.ity 或
im.mature.ness
n.（名詞）