rare
uncommon
rare as rocking horse shit
non-English
superrare
geason
Alwin
rare as a four-leaf clover
ultrarare
semirare
rareish
Isom
seldomly
unique
slip of the tongue
supersubtle
inexpressable
rarer than hens' teeth
Englishy
rare as hen's teeth
unoften
nonvernacular
unvernacular
vaguity
unlikelily
Duke
noneven
one in a million
un-English
once in a blue moon
different
ultrararefied
non-Englishness
rocking horse shit
strictly
undialectical
few and far between
caselessness
seldomness
nondialectal
adialectal
nondialectical
Hebrew
none
unknown
unclearly
scarce
Amata
indescribable
sporadical