Expressions (phrases, clauses, etc.), Adverb (fukushi)
using the strongest words possible; scathingly (criticize, deride, etc.); (praise) to the skies; in the highest possible terms
みんな口を極めて彼女を褒めちぎった。Everybody praised her to the skies.
Also written 口をきわめて【くちをきわめて】