a·typ·i·cal / āˈtipikəl/ • adj. not representative of a type, group, or class: a sample of people who are rather atypical of the target audience there were somewhat atypical results in May and November.DERIVATIVES: a·typ·i·cal·ly adv.

atypical (ay-tip-ik-ăl) adj. not conforming to type. a. antipsychotic see antipsychotic. a. pneumonia pneumonia, caused by such organisms as Mycoplasma pneumoniae, that does not respond to penicillin but does respond to such antibiotics as tetracycline and erythromycin.