Synonyms for Persistent:

adj.

abiding (adjective)
everlasting, lasting, eternal, enduring, continuing, permanent, steadfast.
all (adjective)
relentless, unrelenting.
attentive (adjective)
sedulous.
chronic (adjective)
ceaseless, protracted, perennial, abiding, recurrent, continuous, lingering, long-standing, prolonged, unyielding, sustained, habitual.
consistent (adjective)
unvarying, unfailing, uniform, undeviating, true, even, invariable, homogeneous, unchanging.
constant (adjective)
nonstop, unending, uninterrupted, chronic.
continual (adjective)
repetitive, timeless, regular, consecutive, connected, unbroken, unceasing.
continued (adjective)
abiding, protracted, continued, extended, unceasing, maintained, sustained, interminable, persevering, prolonged.
continuing (adjective)
perdurable.
continuous (adjective)
recurrent, level, consecutive, continuing, straight, continual, undying, unvarying, continuous, indefatigable, unchanging, unbroken, flat, uniform, invariable, endless, monotonous, unchangeable, monolithic, connected, interminable, homogeneous, repeated, cyclical, regular, sequential, unremitting, consistent, gapless, steady, coherent, incessant, lasting, repetitive, nonstop, constant, ceaseless, unending, perennial, habitual, perpetual, featureless, unceasing, even, robot-like, un-intermittent, everlasting, undeviating, seamless.
diligent (adjective)
earnest, sedulous.
durable (adjective)
strong, tough, stable, reliable, perdurable.
firm (adjective)
set, resolved, flat, intent, unchangeable, unwavering, unbending, determined, staunch, unflinching, consistent.
habitual (adjective)
habitual.
hell-bent (adjective)
strong-minded.
importunate (adjective)
importunate.
never-ending (adjective)
undying.
obstinate (adjective)
obstinate.
permanent (adjective)
constant, perpetual, enduring, everlasting, abiding, immutable, unchangeable, fixed, lasting, permanent.
persevering (adjective)
tenacious, indomitable, surviving, enduring, stoical, indefatigable, persevering, brave, unflagging, unfaltering, patient, unwavering, steadfast, lasting, abiding.
persistent (adjective)
perpetual, enduring, relentless, obstinate, tireless, fixed, stubborn, endless, persevering, immovable, interminable, continual, incessant, repeated, steadfast, dogged, resolute, firm, constant, unremitting, tenacious, unflagging, unrelenting, obdurate, insistent, bulldogged, steady, indefatigable.
resolute (adjective)
serious, indomitable, willing, plucky, unyielding, stubborn, implacable, staunch, resolved, unshakeable, true, resolute, headstrong, strong-minded, reliable, strong-willed, set, faithful, zealous, hearty, valiant, decisive, thorough, steady, inexorable, tireless, indefatigable, stern, intent, diligent, bold, tough, unchangeable, loyal, constant, unflinching, dauntless, relentless, steadfast, uncompromising, determined, earnest, persevering, tenacious, bullheaded, committed, deliberate, firm, dedicated, spunky, unwavering, iron-willed, unbending, courageous, dogged, fearless, steely, decided, devoted, insistent, ruthless.
stable (adjective)
continuous, permanent, firm, changeless, stable, steady, set, solid, immovable, steadfast, constant, durable, consistent, invariable.
tenacious (adjective)
enduring, resolute, stiff, bold, persevering, flintlike, dauntless, brave, hard, obdurate, undaunted, faithful, spunky, determined, bullheaded, stony, strong-willed, tenacious, insistent, tireless, courageous, fervent, headstrong, hearty, diligent, unflagging, indefatigable, steadfast, bulldogged, obstinate, indomitable, strong, plucky, tough, staunch, dogged, decisive, true, stubborn, devoted.
unforgettable (adjective)
haunting.
untiring (adjective)
indefatigable.

n.

competitive, sedulous, driven, purposeful, motivated, ambitious. lengthy, importunate, urgent, day in day out, forever, long-drawn-out, continue, Importune. unfailing, uninterrupted, timeless, ongoing, eternal, around the clock, round the clock. long-standing, old, perdurable. chronic, lingering. persistent (noun)
haunting, unrelenting, lasting, unforgettable, relentless, continual.

Other synonyms:

ambitious, round the clock, driven, eternal, long-standing, lingering, long-drawn-out, lengthy, timeless, around the clock. perdurable, uninterrupted, ongoing, importunate, forever. old, unfailing, urgent, competitive. determined
purposeful.
inveterate
chronic.
Other relevant words:
ongoing, ambitious, perdurable, unrelenting, eternal, purposeful, lengthy, forever, uninterrupted, lingering, motivated, continue, importunate, haunting, chronic, competitive, timeless, unforgettable, old, long-drawn-out, driven, sedulous, round the clock, unfailing, Importune, urgent, long-standing.

Usage examples for persistent

  1. His brain would not answer him, save only with that persistent she was a woman and he was a man." – The Belovéd Traitor by Frank L. Packard
  2. Those mentioned above are but fair examples of the persistent and effective work he has done to bring the phonograph to its present state of perfection. – Edison, His Life and Inventions by Frank Lewis Dyer and Thomas Commerford Martin