Antonyms of barrel :
atom, crumb, dot, fleck, flyspeck, fragment, grain, granule, iota, jot, modicum, molecule, mote, nubbin, particle, ray, scintilla, scrap, shred, tittle, whit, smatter, smattering, dash, drop, morsel, shot, piece, portion, section, absence, dearth, famine, lack, paucity, poverty, scarceness, scarcity, shortage, undersupply, want, deficiency, deficit, inadequacy, insufficiency, meagerness, scantiness, scantness, skimpiness, ace, bit, dab, dram, driblet, glimmer, handful, hint, lick, little, mite, mouthful, nip, ounce, peanuts, pinch, pittance, scruple, shade, shadow, smidgen, speck, spot, sprinkle, sprinkling, strain, streak, suspicion, tad, taste, touch, trace.
Examples of usage:
Then he picked up the barrel top and looked at it in an astonishment that gave way presently to something like profound admiration. "Jane Lends A Hand", Shirley Watkins.
And there was hunger in his face, in her face, and still more in the gleaming eyes of the children round the barrel. "Stories and Pictures", Isaac Loeb Peretz.
But the count seized him by the collar with one hand and with the other clutched the barrel of the revolver. "The Prussian Terror", Alexandre Dumas.