Impossible to repress or control:
— An irrepressible chatterbox.

synonym: uncontrollable.

Roget 173: violent, vehement; warm; acute, sharp; rough, rude, ungentle, bluff, boisterous, wild; brusque, abrupt, waspish; impetuous; rampant.    turbulent; disorderly; blustering, raging etc. v.; troublous^†, riotous; tumultuary^†, tumultuous; obstreperous, uproarious; extravagant; unmitigated; ravening, inextinguishable, tameless; frenzied etc. (insane) 503.    desperate etc. (rash) 863; infuriate, furious, outrageous, frantic, hysteric, in hysterics.    fiery, flaming, scorching, hot, red-hot, ebullient.    savage, fierce, ferocious, fierce as a tiger.    excited etc. v.; unquelled^†, unquenched, unextinguished^†, unrepressed, unbridled, unruly; headstrong, ungovernable, unappeasable, immitigable, unmitigable^†; uncontrollable, incontrollable^†; insuppressible, irrepressible; orgastic, orgasmatic, orgasmic.    spasmodic, convulsive, explosive; detonating etc. v.; volcanic, meteoric; stormy etc. (wind) 349.    ... show more

Roget 748: free, free as air; out of harness, independent, at large, loose, scot-free; left alone, left to oneself.    in full swing; uncaught, unconstrained, unbuttoned, unconfined, unrestrained, unchecked, unprevented^†, unhindered, unobstructed, unbound, uncontrolled, untrammeled.    unsubject^†, ungoverned, unenslaved^†, unenthralled^†, unchained, unshackled, unfettered, unreined^†, unbridled, uncurbed, unmuzzled.    unrestricted, unlimited, unmitigated, unconditional; absolute; discretionary etc. (optional) 600.    unassailed, unforced, uncompelled.    unbiassed^†, spontaneous.    free and easy; at ease, at one's ease; degage [Fr.], quite at home; wanton, rampant, irrepressible, unvanquished^†.    exempt; freed etc. 750; freeborn; autonomous, freehold, allodial^†; gratis etc. 815; eleutherian^†.    unclaimed, going a begging.    ... show more

Roget 825: excitable, easily excited, in an excitable state; high-strung; irritable etc. (irascible) 901; impatient, intolerant.    feverish, febrile, hysterical; delirious, mad, moody, maggoty-headed.    unquiet, mercurial, electric, galvanic, hasty, hurried, restless, fidgety, fussy; chafing etc. v.. startlish^†, mettlesome, high-mettled^†, skittish.    vehement, demonstrative, violent, wild, furious, fierce, fiery, hot-headed, madcap.    overzealous, enthusiastic, impassioned, fanatical; rabid etc. (eager) 865.    rampant, clamorous, uproarious, turbulent, tempestuous, tumultuary^†, boisterous.    impulsive, impetuous, passionate; uncontrolled, uncontrollable; ungovernable, irrepressible, stanchless^†, inextinguishable, burning, simmering, volcanic, ready to burst forth, volatile.    excited, exciting etc. 824.    ... show more