What does в сложн. сл. mean in Russian dictionary?

Question

What does в сложн. сл. mean in below screenshot (highlighted with red rectangle)? Source

Answer 1

"в сложн. сл." stands for "в сложных словах" ("in compound words").

For example, "трехдюймовый" - compound word (сложное слово) consisting of two words: "трех-" and "-дюймовый".