unpremeditated 

英汉解释

adj. 无预谋的；偶然的

反义词

a.   premeditated

参考例句

1. All growth is a leap in the dark, a spontaneous unpremeditated act without the benefit of experience.
所有的成长是一种在黑暗中的跳越，一种自发性非预谋没有经验的益处的行动。
2. There was fire in her and throughout her; she seemed the unpremeditated offshoot of a passionate moment.
她浑身上下有一团火，向四下发散着，象是在激情时刻不期而孕的一个子嗣。
3. There was fire in her and throughout her: she seemed the unpremeditated offshoot of a passionate moment.
她浑身上下有一团火，向四下发散着，像是在激情时刻不期而孕的一个子嗣。

英英解释

adj.
  1. not prepared or planned in advance
  2. not premeditated

网络释义

unpremeditated
非故意的; 无预谋的; 未经事先考虑的; 无预谋;
unpremeditated crime
非预谋罪行 非预谋罪行; 非预谋罪行;
Slight unpremeditated Words are borne
不加思索的轻率话语;