In my personal classification, certain words are assigned a rating based on some criteria. The top rating is AA, and below it the ratings go from A all the way down to Z. Seventeen AA-class words are listed below.
ants arms ingots limn mars nark nonvariant pi rams rank rhino rip san sulk suns tans wart
Most words are unrated, whereas some words may qualify for multiple ratings. For example, pair would qualify for both an A-class and an S-class rating.
To my knowledge, there is exactly one word with a Z rating. What is it?
The AA rated words are words which
which anagram to a country capital with AA appended.
The seventeen are
ants - Astana, arms - Asmara, ingots -Santiago, limn - Manila, mars - Asmara, nark - Ankara, nonvariant - Antananarivo, pi - Apia, rams - Asmara, rank - Ankara, rhino - Honiara, rip - Praia, san - Sanaa, sulk - Lusaka, suns - Nassau, tans - Astana, wart - Tarawa.
Following this rule a Z rated word is
barge - Zagreb is the capital of Croatia.