Synonyms for Mannerism:

n.

schtick, behavior, inclination, conduct, posture, outlook, spirit, human nature. honest, true. air (noun)
property.
habit (noun)
Familiarity, daily grind, disposition, rut, conventionality, acclimation, tendency, tradition, custom, routine, habit, temperament, fixed ways, treadmill, trait, way of life, leaning, addiction, wont, regularity, second nature, instinct.
idiosyncrasy (noun)
study at pose.
mannerism (noun)
pose, idiosyncrasy, affectation, foible.
peculiarity of how someone behaves, acts (noun)
quirk, habit, idiosyncrasy, air, pose, trait, characteristic, pretension, affectation, foible.
phrase (noun)
figure of speech, cliche, sentence, clause, phraseology, terminology, motto, epigram, euphemism, idiom, expression, catchphrase, proverb, adage, metaphor, phrase, maxim, locution, paragraph, Verbalism, slogan.
pretension (noun)
charade, fakery, claim, imposture, artificiality, forgery, cover, imitation, front, impersonation, device, masquerade, bluff, gimmick, pretense, air, disguise, deceit, affectation, falseness, stage, counterfeit, show, pretension, pose, facade, guise, ostentation, fraud.
specialty (noun)
stamp, Discriminant, keynote, quality, hallmark, specialization, cachet, particularity, individuality, forte, specialty, quirk, characteristic, peculiarity, figure, property, feature, way, definiteness, flavor, mark, difference, idiosyncrasy.

Other synonyms:

Other relevant words:
true, inclination, outlook, conduct, posture, schtick, foible, spirit, behavior, honest.