Synonyms for Presuming:

adj.

arrogant (adjective)
overconfident, presumptuous, proud, egotistic.
friendly (adjective)
Familiar.
self-confident (adjective)
presumptuous.
trusting (adjective)
believing.

n.

brash, Familiar, audacious, contumelious, flip, assumptive, forward, uppish, fresh, pert, courtesy, nervy, bold, cheeky, pushy, sassy, insolent, snippy, smart, smart-alecky, Snippety, overconfident, uppity, impudent, boldfaced, attitude, brazen, presumptuous, impertinent, saucy, wise, brassy, Malapert. arrogant (noun)
proud, presumptuous, egotistic.

v.

believing (verb)
Deeming, Affirming, gathering, holding, professing, assuming, judging, accepting, concluding, understanding, assenting, trusting, Maintaining, Declaring, taking for granted, Surmising, giving faith, Crediting, believing, putting faith in, Supposing.
calculating (verb)
dividing, Systematizing, Multiplying, Assessing, Approximating, programming, reckoning, scheming, Summing, determining, rating, Estimating, quantizing, accounting, computing, scheduling, planning, Adding, counting, Gauging, rationalizing, appraising, Considering, weighing, scoring, guessing, Tallying, Totaling, measuring, evaluating, calculating, figuring, Deducing, Plotting, thinking, Triangulating, ranking, quantifying, Enumerating, Inferring, Valuing, studying.
expecting (verb)
Anticipating, Contemplating, foreseeing, Foreknowing, envisioning, Expecting, Apprehending, Envisaging, Presupposing, Awaiting, Suspecting, Imagining, foreboding, Dreading.
hoping (verb)
Intending, dreaming of, wishing, Relying, Hoping, Desiring, aspiring, yearning, wanting.
supposing (verb)
Theorizing, fantasizing, hypothesizing, Conceiving, Prophesying, Speculating, philosophizing, Conjecturing.

Other synonyms:

Snippety, cheeky, sassy, smart-alecky, contumelious, pushy, boldfaced. egotistic, assumptive, brassy, uppity, presumptuous, nervy, snippy, uppish, impertinent, Malapert, overconfident, impudent, saucy. brazen, forward, pert, brash. bold, insolent, smart, audacious. fresh. wise. Other relevant words:
brassy, assumptive, brash, sassy, saucy, cheeky, brazen, forward, insolent, wise, Malapert, snippy, fresh, bold, uppish, boldfaced, audacious, pushy, proud, overconfident, flip, smart, smart-alecky, Familiar, presumptuous, pert, impudent, impertinent, Snippety, nervy, contumelious, uppity.

Usage examples for Presuming

  1. I can't say as much for his son- a presuming fellow, who,- ha! – The Lady of Lyons or Love and Pride by Edward Bulwer Lytton
  2. Will you think me impertinent, presuming inquisitive?" – The Rosary by Florence L. Barclay
  3. That is why I felt I must ask you to forgive me for presuming to blame you. – By Right of Purchase by Harold Bindloss