meQ means "be on fire" and meQmoH means "set on fire".

From KGT (p191-192):

meQ ("burn") / mIQ ("deep-fry")

to'waQ meQ vutwI'. ("The cook burns the tendon.")
to'waQ mIQ vutwI'. ("The cook deep-fries the tendon.")

The verb meQ is used several times in the paq'batlh. It's also been used several times previously, elsewhere. I presented Dr. Okrand with all of the usages of meQ and also several possible definitions corresponding to those usages: "burn, be on fire", "burn, cause to be on fire", "be burnt". He wrote that it would normally have the first definition (and thus meQmoH is needed to express setting something on fire). However, due to the influence of mIQ, meQ is used differently in the context of food preparation. Thus, you could say to'waQ meQ vutwI' "the cook burns the tendon" and Ha'DIbaHmey meQ "burnt animals", but not *juH qachDaj meQ "he burned his house" or *qach meQ "a burnt building" (I guess unless you're talking about someone who eats buildings as a part of their cuisine). The paq'batlh consistently uses meQ to mean "be on fire" and meQmoH to mean "set on fire".

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