Rain pattern

Rain pattern is a family of military camouflage patterns used by Warsaw Pact countries such as Poland, Czechoslovakia, East Germany, and Bulgaria. They are characterised by the presence of many closely spaced vertical streaks resembling falling rain, printed over a background which is often of a single colour, but may itself be disruptively patterned.

The 1931 German splittermuster, used extensively in many variants in the Second World War, incorporated a "rain" element as well as a bold disruptive pattern of splotches. Poland appears to have been the first to introduce a pure rain pattern. It was followed by Czechoslovakia in 1963.

...
Wikipedia