uncommon
semirare
rareish
rare
Isom
geason
rare as a four-leaf clover
unique
non-English
Alwin
superrare
Englishy
rare as rocking horse shit
slip of the tongue
impostor
Shakespeare
inexpressable
Englishism
seldomness
vaguity
potty
Duke
limitedly
strictly
Globish
nonvernacular
one in a million
unvernacular
rarer than hens' teeth
seldomly
Hebrew
obscurely
unlikelily
semioccasional
nuance
rare as hen's teeth
Melodie
peculiar
antrin
semioccasionally
nonlexical
vernaculate
alexical
unlexical
caseless
sporadically
duckspeak
semiobscure
Amata
strain