形容詞 erratic:

1. having no fixed course
   同義詞：planetary, wandering
2. liable to sudden unpredictable change
   同義詞：fickle, mercurial, quicksilver
3. likely to perform unpredictably- Osbert Lancaster
   同義詞：temperamental

1. An empty-headed, silly, often erratic person.
   古怪的人傻的、愚蠢的并且通常很古怪的人
2. This clock is rather erratic.
   這個鐘不太準。
3. Deliveries of goods are erratic.
   不按規(guī)定送貨。
4. The singer gave an erratic performance.
   演唱者未唱出水平。

er.rat.ic

adj.（形容詞）
Having no fixed or regular course; wandering.
飄忽不定的：沒有固定的或規(guī)律性的行蹤；游蕩
Lacking consistency, regularity, or uniformity.
無規(guī)律的：缺乏連續(xù)性、規(guī)律性或一致性
Deviating from the customary course in conduct or opinion; eccentric:
古怪的：在行為與觀點上與習(xí)慣的作法偏離；偏執(zhí)的：
例句：
erratic behavior.
古怪的行為

來源：
Middle English erratik
中古英語 erratik
from Old French erratique
源自 古法語 erratique
from Latin err3ticus
源自 拉丁語 err3ticus
from err3re [to wander] * see ers-
源自 err3re [漫游] *參見 ers-

【引伸】
errat.ically
adv.（副詞）
errat.icism