This is the 12860th most frequent Russian word.
лабораторного
"Лабораторного" means "of the laboratory" or "laboratory-related" in English.
In this sentence, "лабораторного" functions as the genitive case of the adjective "лабораторный" modifying the noun "крысу" to describe a special rat used for laboratory purposes.
Он изучал лабораторного крысу на уроке биологии.
He studied a laboratory rat in biology class.
Here, "лабораторного" denotes the genitive case to describe the department related to laboratory work in chemistry.
Она работала в лабораторного отдела химии.
She worked in the laboratory department of chemistry.
In this example, "лабораторного" is in the genitive case and modifies "оборудования" to specify that the equipment is used in laboratories.