The Collaborative International Dictionary of English v.0.48:

Ceaseless \Cease"less\, a.
   Without pause or end; incessant.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ceaseless \Cease"less\, adv.
   Without intermission or end.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ceaseless
    adj 1: uninterrupted in time and indefinitely long continuing;
           "the ceaseless thunder of surf"; "in constant pain";
           "night and day we live with the incessant noise of the
           city"; "the never-ending search for happiness"; "the
           perpetual struggle to maintain standards in a democracy";
           "man's unceasing warfare with drought and isolation";
           "unremitting demands of hunger" [syn: ceaseless,
           constant, incessant, never-ending, perpetual,
           unceasing, unremitting]

Moby Thesaurus II by Grady Ward, 1.0:

86 Moby Thesaurus words for "ceaseless":
   ageless, amaranthine, articulated, catenated, chattering,
   coeternal, concatenated, connected, constant, continual, continued,
   continuing, continuous, cyclical, dateless, direct, endless,
   eternal, eterne, ever-being, ever-durable, ever-during,
   everlasting, everliving, featureless, gapless, immediate,
   immemorial, immortal, incessant, indestructible, infinite,
   interminable, joined, jointless, linked, machine gun, monotonous,
   never-ceasing, never-ending, nonstop, nonterminating, nonterminous,
   olamic, oscillating, perdurable, perennial, periodic, permanent,
   perpetual, pulsating, rapid, recurrent, regular, repeated,
   repetitive, round-the-clock, running, seamless, sempiternal,
   serried, smooth, stable, staccato, steady, straight, stuttering,
   sustained, timeless, twenty-four-hour, unbroken, unceasing,
   unchanging, undifferentiated, unending, uniform, unintermitted,
   unintermittent, unintermitting, uninterrupted, unrelieved,
   unremitting, unstopped, unvarying, vibrating, without end