不可撤销信用证

bù kě chè xiāo xìn yòng zhèng

irrevocable letter of credit

不

bù

no; not so

可

kě

(prefix) can; may; able to; -able

撤

chè

to remove; to take away

销

xiāo

to melt (metal)

信

xìn

letter

用

yòng

to use; to make use of; to employ

证

zhèng

certificate