(pl.alibis)
1- a claim or piece of evidence that one was elsewhere when an act, typically a criminal one, is alleged to have taken place（尤指犯罪行为发生时某人）不在现场的证词（或证据）：
she has an alibi for the whole of yesterday evening
她有昨夜一整晚不在场的证据
mass noun a defence of alibi.不在现场的辩护。
1.1
- informal an excuse or pretext〈非正式〉借口, 托辞：
a catch-all alibi for failure and inadequacy.
一个对失败和不足的全能托辞。
(alibis, alibied, alibiing)with obj.
- informal offer an excuse or defence for (someone), especially by providing an account of their whereabouts at the time of an alleged act〈非正式〉为（某人）作证, 辩护（尤指提供案发当时其行踪信息）：
her friend agreed to alibi her.
她的朋友答应为她作证。
The word alibi, which in Latin means 'elsewhere'， has been used since the 18th century to mean 'an assertion by a person that he or she was elsewhere'. In the 20th century a new sense arose (originally in the US) with the meaning 'an excuse'. This use is an example of a fairly common and natural extension of the core meaning， and， though widely accepted in standard English， it is still regarded as incorrect by some traditionalists.
词源
late 17th cent. （as an adverb in the sense 'elsewhere'）： from Latin， 'elsewhere'. The noun use dates from the late 18th cent.