名詞 retard:

1. a person of subnormal intelligence
   同義詞：idiot, imbecile, cretin, moron, changeling, half-wit

動詞 retard:

1. slow the growth or development of
   同義詞：check, delay
2. cause to move more slowly or operate at a slower rate
3. be delayed
4. lose velocity; move more slowly
   同義詞：decelerate, slow, slow down, slow up

1. Cold weather retards the growth of the crops.
   寒冷的天氣妨礙了莊稼生長。
2. Lack of sun retards plant growth.
   光照不足則植物生長緩慢。

re.tard

v.（動詞）
re.tard.ed,re.tard.ing,re.tards
v.tr.（及物動詞）
To cause to move or proceed slowly; delay or impede.
減速，拖?。菏挂苿踊蛐羞M緩慢；延遲或阻礙
v.intr.（不及物動詞）
To be delayed.See Synonyms at delay
受到延遲參見 delay
n.（名詞）
A slowing down or hindering of progress; a delay.
減速，放慢：前進步伐的減慢或阻礙；延遲
Music A slackening of tempo.
【音樂】 拍子的減慢
[rô.tôrd.] Offensive Slang Used as a disparaging term for a mentally retarded person.
[rô.tôrd.] 【無禮用語】 【俚語】 智力遲鈍者：用作精神遲鈍者的貶稱

來源：
Middle English retarden
中古英語 retarden
from Old French retarder
源自 古法語 retarder
from Latin retard3re
源自 拉丁語 retard3re
re- [re-]
re- [表示.再.]
tard3re [to delay] from tardus [slow]
tard3re [延遲] 源自 tardus [慢的]

【引伸】
retard.er
n.（名詞）