The full phrase is: "Гло́кая ку́здра ште́ко будлану́ла бо́кра и курдя́чит бокрёнка" (Glokaya kuzdra shteko budlanula bokra i kurdyachit bokryonka).
In the phrase, all word stems (glok-, kuzdr-, shtek-, budl-, bokr-, kurd-) are meaningless, but all affixes are real, used in a grammatically correct way and — which is the point — provide enough semantics for the phrase to be a perceived description of some dramatic action with a specified plot but with unknown actors.
[1] An English translation (only syntax and no semantics) could be: "The glocky kuzdra shteckly budled the bocker and is kurdyaking the bockerling."
Shcherba used it in his lectures in linguistics to emphasize the importance of grammar in acquiring foreign languages.
In particular, they noticed that Uspensky's "deciphering" of the phrase is non-unique, due to high variability of the syntax of the Russian language.