The linguistic and axiological potential of unofficial urbanonyms reflecting the realities of the urban environment as a design space is evaluated. The research tasks include identifying typical and non-standard objects and motifs of evaluative urbanonymic nomination, developing optimal methods for describing interregional nominative parallels and unique slang terms in the dictionary of unofficial urbanonyms. The material sources consist of dictionaries of youth slang, author’s archives of spoken language, and internet communications (2010—2024). The semantics of slang terms-urbanonyms were clarified using componential and contextual analysis methods. Parameters of their lexical description were developed using the method of lexicographical construction. Based on slang material from Pskov and St. Petersburg involving unofficial urbanonyms from Ufa, Volgograd, Novosibirsk, and other cities, the evaluative attitude of nominators towards design projects embodied in architectural structures, memorial objects, street sculpture, and monumental painting is demonstrated. Interpretations, comments, and contextual illustrations in the presented fragments of the projected dictionary reveal the specificity of the nominator’s imagery associations when implementing various ways of slang formation: playful transformations of official names, references to precedent phenomena, metonymic and metaphorical transfers and their combinations.