All business are to be transacted against confirm and irrecoverable letter of credit.是什么意思？

All business are to be transacted against confirm and irrecoverable letter of credit.

所有交易都应采用保兑的不可撤销信用证支付.

all

adj. 全部的，一切的，各种的，极度的，尽量的；pron. 全部，一切，每个人，每件东西，全部情况；adv. 全部地，完全地，每个，非常；n. 全体，[常作A-]整体，[常与my, your, his, her等连用]（某人）所有的一切；

例句
Many parents simply abdicate all responsibility for their children.
许多父母对孩子简直是完全撒手不管。

business

n. 商业，交易，生意，事务，业务，职业，行业；

例句
Many men still have difficulty accepting a woman as a business partner...
许多男性仍然无法接受女性商业伙伴。

are

vi. （用于第二人称单复数现在时，第一、三人称复数现在时）是；n. 公亩（等于100平方米）；

例句
We are scared to abandon ourselves to our feelings in case we seem weak or out of control.
我们不敢放纵自己的情感，以免显得太过软弱或缺乏自制。

to

prep. 向，朝着，到，关于，属于；adv. 朝一个方向的，到某种状态，关闭；

例句
I suggest you leave it to an expert...
我建议你把它留给专家来解决。

be

v. 是，有，存在，做，成为，发生；aux. 用来表示某人或某物即主语本身，用来表示某人或某物属于某一群体或有某种性质；

例句
The older child should be able to prepare a simple meal...
那个年纪稍大的孩子应当会做一顿简单的饭菜。

transacted

--

例句
All business are to be transacted against confirm and irrecoverable letter of credit.
所有交易都应采用保兑的不可撤销信用证支付.

against

prep. 反对，对…不利，紧靠，以防；

例句
His hand brushed against hers; it could have been either accidental or deliberate.
就在有意无意间，他的手轻轻拂过她的手。

confirm

vt. [法]确认，批准，证实，使有效，使巩固；

例句
Further scans are required to confirm the diagnosis of an abnormality...
需要进一步扫描来确诊是否出现异常病变。

and

conj. 和，与，而且，于是，然后，因此；

例句
I spend a lot on expensive jewelry and clothing...
我花很多钱购买昂贵的首饰和衣服。

irrecoverable

adj. 无可挽救的，不可弥补；

例句
The depression, however, caused many irrecoverable accounts and Dr. Sim started to run up debts.
然而经济萧条造成许多呆帐,他也因此负债累累.

letter

n. 信，证书，许可证，字母，文字，字面意义；vt. 用字母标明，写字母于，加标题；vi. 写印刷体字母；

例句
Naylor acknowledged, in a letter to the judge, that he was a drug addict...
内勒在给法官的信中承认自己吸毒。

of

prep. 关于，属于…的，由…制成；aux. 助动词 [非标准用语、方言] =have [主用于虚拟语气]；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

credit

n. 信誉，信用，[金融]贷款，荣誉，学分；vt. 相信，信任，归功于，[会]记入贷方，赞颂；

例句
People were betting on a further easing of credit conditions.
人们期待着贷款条件进一步放宽。