laborious

1 involved in often constant activity the volunteers have been commendably laborious in their cleanup of the beach Synonyms active, assiduous, bustling, diligent, employed, engaged, hopping, industrious, busy, occupied, sedulous, tied-up, workingRelated Words knee-deep, swamped; animated, astir, buzzing, flourishing, happening, humming, lively, thriving, vibrant; absorbed, concentrating, engrossed, focused (also focussed), immersed, intent, preoccupied; alive, functional, functioning, going, living, operating, operational, operative, running; energetic, vigorous; hardworking; indefatigable, tireless, untiringNear Antonyms free; asleep, dormant, latent, lifeless, quiescent, sleepy; inert, passive; dead, dull, slow; inoperative, nonoperatingAntonyms idle, inactive, unbusy, unemployed, unoccupied

2 requiring considerable physical or mental effort the laborious task of cleaning up the oil spill Synonyms arduous, Augean, backbreaking, challenging, demanding, difficult, effortful, exacting, formidable, grueling (or gruelling), heavy, hellacious, herculean, killer, hard, moiling, murderous, pick-and-shovel, rigorous, rough, rugged, severe, stiff, strenuous, sweaty, tall, testing, toilsome, tough, uphillRelated Words abstract, abstruse, complex, complicated, elusive, hairy, insoluble, intricate, involved, knotty, opaque, problematic (also problematical), recondite, serious, spiny, stubborn, thorny, ticklish, tricky; bruising, burdensome, exhausting, labored, onerous, oppressive, stressful, taxing, tight, trying; annoying, bothersome, distressing, irksome, troublesome, vexatious; grievous, grim, strict, stringent; brutal, cruel, inhuman, painfulNear Antonyms achievable, clear, doable, elementary, manageable, uncomplicated; comforting, gentle, painless, relaxed, smooth, soothing; accessible, friendly, idiotproof, user-friendlyAntonyms cheap, easy, effortless, facile, light, mindless, simple, soft, undemanding

3 requiring much time, effort, or careful attention that report is the product of months of laborious research Synonyms arduous, burdensome, challenging, exacting, grueling (or gruelling), killing, demanding, onerous, persnickety, taxing, toilsomeRelated Words difficult, formidable, hard, herculean, rough, rugged, stiff, strenuous, testing, tough; oppressive, trying; rigid, rigorous, severe, stern, strict, stringentNear Antonyms easy, effortless, facile, simple, smoothAntonyms light, nondemanding, unchallenging, undemanding