Atypical is a related term of rare.
As adjectives the difference between atypical and rare
is that
atypical is not conforming to the normal type while
rare is (cooking|particularly meats) cooked very lightly, so the meat is still red (in the case of steak or beef in the general sense) or
rare can be very uncommon; scarce or
rare can be (obsolete) early.
As a noun atypical
is (pharmacy) an atypical antipsychotic.
As a verb rare is
(us|intransitive) to rear, rise up, start backwards.