Definition of earnest :
1. Ardent in the pursuit of an object; eager to obtain or do; zealous with sincerity; with hearty endeavor; heartfelt; fervent; hearty; - used in a good sense; as, earnest prayers.
2. Intent; fixed closely; as, earnest attention.
3. Serious; important.
4. Seriousness; reality; fixed determination; eagerness; intentness.
5. Something given, or a part paid beforehand, as a pledge; pledge; handsel; a token of what is to come.
6. Something of value given by the buyer to the seller, by way of token or pledge, to bind the bargain and prove the sale.
7. To use in earnest.
importunate, purposeful, high-priced, good, heartfelt, beloved, pricy, hot, pricey, businesslike, momentous, heavy, attitude, impetuous, near, keen, staid, impatient, severe, work, in earnest, warm, god-fearing, glowing, desirous, no-nonsense, devout, darling, weighty, longing, anxious, sobersided, vehement, dear, yearning, important, costly
serious (part of speech: adjective)
resolute (part of speech: adjective)
indefatigable, inexorable, persevering, committed, resolute, determined, fearless, true, persistent, ruthless, bold, stubborn, unwavering, thorough, unyielding, unshakeable, dedicated, unbending, courageous, deliberate, decided, tough, decisive, tireless, indomitable, implacable, devoted, reliable, loyal, stern, uncompromising, relentless, diligent, staunch, steely, strong-minded, bullheaded, faithful, strong-willed, tenacious, steady, constant, intent, plucky, headstrong, valiant, steadfast, serious, unflinching, unchangeable, firm, dogged, resolved, iron-willed, set, dauntless, insistent, spunky
truthful (part of speech: adjective)
vigorous (part of speech: adjective)
fervent, energetic, burning, spirited, emphatic, hearty, animated, full-blooded, passionate, potent, mettlesome, sprightly, fiery, zestful, frisky, impassioned, agitated, afire, enthusiastic, prolific, puissant, excited, peppy, zealous, industrious, zippy, strenuous, strong, vigorous, eager, lively, virile, powerful, lusty, active, ardent, exuberant, ablaze
willing (part of speech: adjective)
cooperative, tame, agreeable, malleable, flexible, submissive, compliant, amenable, receptive, acquiescent, pliant, persuadable, pliable, adaptable, yielding, tractable, ready, willing, plastic, biddable, assenting, susceptible, ductile