abstruseness, arduousness, bothersomeness, burdensomeness, complication, convolution, crabbedness, crampedness, deepness, difficultness, difficulty, esoterica, hairiness, hardness, inscrutability, intricacy, involvement, knottiness, laboriousness, onerousness, oppressiveness, profoundness, profundity, reconditeness, rigor, rigorousness, ruggedness, strenuousness, toilsomeness, toughness, troublesomeness