The article presents a part of the research on the Russian and Polish lexical units containing the глуп-/głup- root. The noun, verb and adverb forms have been analysed from the point of view of their meanings and the functional, stylistic and derivational properties. That is why the research material includes the contemporary units such as colloquialisms and lexemes of the restricted usage (archaisms and linguistic variants) which occur in both languages. The lexical units have been selected from the contemporary and historical explanatory and etymological dictionaries as well as from the former and dialectal lexis.