You are presented with five groups of five words. All of the letters in each word share a common trait, except for one. The rule governing which letter is different is consistent within each group.
The unique letters in each group spell a word. Applying the group's rule to that word produces a single meta-letter. Use the five meta-letters to find the meta-word which answers the title question.
asia maui scratch eerie auto blacklight foreshadow dynasty napalm roleplaying gasped deadbeat horticulturist bagpipe decoded corrupt snowplow nervous yawn challengeable perpetrator without falafel equator tidy
Bonus: What is the meta-meta-letter?