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