In Russian culture, blat (Russian: блат) is a form of corruption which is the system of informal agreements, exchanges of services, connections, Party contacts, or black market deals to achieve results or get ahead.
In the Soviet republics, blat, a form of corruption, was widespread because of the common deficit of consumer goods and services. In Soviet times the price of consumer goods was dictated by the state rather than set by the free market which resulted in a consumer goods deficit leading to corruption. Blat was used to gain a prestigious position or a rewarding job or an overseas posting or enroll in a prestigious major in university bypassing fair and just selection processes.
The system of blat can be seen as an example of social networks with some similarities to networking (especially 'good ol' boy' networks) in the United States, old boy networks in the United Kingdom and the former British Empire, or guanxi in China.
However, the noun blatnoy (блатной) has a criminal meaning in Russian and it relates to a status in the criminal world. It usually means a member of a thief gang.
The word was primarily used to describe networks, when people made each a favour in exchange for another favour.
According to Max Vasmer, the origin of the word blat is the Yiddish blatt, meaning a "blank note" or a "list". However, according to both Vasmer and N. M. Shansky, blat may also have entered into Russian as the Polish loanword blat, a noun signifying "someone who provides an umbrella" or a "cover". The word became part of Imperial Russian criminal slang in the early 20th century, where it signified relatively minor criminal activity such as petty theft.