disconcert

动词 disconcert:

1. cause to feel embarrassment
   同义词：confuse, flurry, put off
2. cause to lose one's composure
   同义词：upset, discompose, untune, discomfit

1. He was disconcerted to find the other guests formally dressed.
   他看到其他客人都穿得正正经经的，觉得很尴尬。

dis.con.cert

v.tr.（及物动词）
dis.con.cert.ed,dis.con.cert.ing,dis.con.certs
To upset the self-possession of; ruffle.See Synonyms at embarrass
使…仓皇失措；使窘迫参见 embarrass
To frustrate (plans, for example) by throwing into disorder; disarrange.
通过扰乱而挫败（如计划）；使混乱

来源：
Obsolete French disconcerter
已废法语 disconcerter
from Old French desconcerter
源自 古法语 desconcerter
des- [dis-]
des- [表示.不，打消.等意思]
concerter [to bring into agreement] from Old Italian concertare
concerter [达成协议] 源自 古意大利语 concertare

【引伸】
dis.concert.ingly
adv.（副词）