Synonyms for True:

adj.

aboveboard (adjective)
veracious.
artless (adjective)
ingenuous.
correct (adjective)
righteous.
horizontal (adjective)
level.
liege (adjective)
liege.
loyal (adjective)
fast, liege, worthy, firm, honorable, steadfast, creditable, reliable, faithful, devoted, resolute, estimable, right-minded, upright, allegiant, steady, constant, staunch, dedicated, unaffected.
precise (adjective)
accurate.
real (adjective)
solid, authentic, veritable, honest, genuine, tangible, actual, factual, substantial, sincere, concrete, real.
real, valid; concordant with facts (adjective)
actual, kosher, right, sincere, precise, factual, honest, undeniable, veritable, pure, natural, exact, indubitable, authentic, undoubted, accurate, genuine, bona fide, veracious, correct, veridical, unquestionable.
resolute (adjective)
decisive, hearty, valiant, reliable, tireless, iron-willed, willing, stern, unwavering, resolute, diligent, tenacious, steadfast, unbending, devoted, bullheaded, unyielding, stubborn, strong-minded, implacable, ruthless, inexorable, spunky, staunch, plucky, indefatigable, intent, bold, dedicated, serious, faithful, thorough, steady, courageous, firm, tough, dogged, headstrong, constant, uncompromising, persevering, decided, deliberate, insistent, persistent, zealous, unflinching, steely, relentless, set, committed, strong-willed, determined, indomitable, loyal, fearless, earnest, unshakeable, resolved, unchangeable, dauntless.
respectable (adjective)
irreproachable, moral, fair, righteous, angelical, pure, principled, saintly, virtuous, good, right-minded, law-abiding, respectable, forthright, noble, estimable, creditable, unimpeachable, untarnished, blameless, honorable, honest, upstanding, worthy.
sound (adjective)
proven.
tenacious (adjective)
enduring, bullheaded, persistent, steadfast, persevering, headstrong, indefatigable, diligent, bulldogged, undaunted, fervent, staunch, dauntless, resolute, stony, hard, hearty, indomitable, flintlike, obdurate, determined, obstinate, insistent, bold, stiff, decisive, strong-willed, courageous, spunky, brave, dogged, tough, stubborn, devoted, faithful, tireless, plucky, strong, tenacious, unflagging.
true (adjective)
definite, honest, certain, factual, absolute, right, gospel, proven, axiomatic, veracious, authentic.
veracious (adjective)
ingenuous, accurate, authentic, correct, factual, honest, veracious, genuine.
veridical (adjective)
veridical.

n.

definitely, undeniable. kosher, valid, real world, physical, apparent. develop, be actualized, to be sure, happen, let's face it, I must confess, my bad, actually, come about. reputable, consistent, rigorous, exact, sound, veridical, as good as your word, precise. horizontal, perpendicular, level, incorruptible, vertical, upright, straight-shooting, erect, flat. indubitable, unquestionable, bona fide, undoubted. convincing, credible. natural, true-life, realistic, naturalistic, lifelike. continue, trust, liege, fast, allegiant. heartfelt, unmannered, unaffected. accurate (noun)
plumb, valid, exact, precise.
loyal (noun)
diehard, stalwart.

Other synonyms:

rigorous, unaffected. fast. genuine
valid.
in truth
actually.
loyal
diehard, stalwart.
trustworthy
sound.
Other relevant words:
bona fide, veridical, sound.