imbecile

詳細解釋：

im.be.cile

n.（名詞）
A stupid or silly person; a dolt.
蠢人；傻瓜
A person whose mental acumen is well below par.
低能者：智力遠在常態之下的人
A person of moderate to severe mental retardation having a mental age of from three to seven years and generally being capable of some degree of communication and performance of simple tasks under supervision. The term belongs to a classification system no longer in use and is now considered offensive.
弱智者：有中度到嚴重精神障礙的人，有三到七歲的智力年齡，在指導下通常能做某種程度的交流並能完成簡單的任務。這個術語屬於一個已停用的區分系統，現在被認為是攻擊性的
adj.also （形容詞） 也作
imbecilic
Stupid; silly.
愚蠢的；傻的
Well below par in mental acumen.
弱智的：智力遠在常態之下的

來源：
From obsolete French imbécille [weak, feeble]
源自 已廢法文 imbécille [軟弱的，微弱的]
from Old French
源自 古法文
from Latin imbôcillus
源自 拉丁語 imbôcillus
in- [not] * see in-
in- [不] *參見 in-
possibly bacillum [staff] [diminutive of] baculum [rod] * see bak-
可能為 bacillum [棍棒] [] baculum的小後綴 [棒條] *參見 bak-

【引伸】
im.becilely
adv.（副詞）