on even keel (adverb) evenly: on an even plane
Sinonime: baffling, enigmatic, incomprehensible, indecipherable, indescribable, inexplainable, inscrutable, insoluble, mysterious, mystifying, obscure, odd*, peculiar, puzzling, strange, unaccountable, undefinable, unfathomable, unintelligible, unsolvable
Antonime: irregularly,
roughly, unevenly