The term 'apartment pest' refers to a type of insect or rodent that can be found in residential dwellings. Roach (5 letters) is a common apartment pest, as it is an insect that can survive in a variety of environments and reproduce quickly. UNIT (4 letters) is another type of apartment pest, which can refer to any type of small mammal, such as mice or rats, that can enter a dwelling through small openings or cracks.