knock
     n 1: the sound of knocking (as on a door or in an engine or
          bearing); "the knocking grew louder" [syn: {knocking}]
     2: negative criticism [syn: {roast}]
     3: a vigorous blow; "the sudden knock floored him"; "he took a
        bash right in his face"; "he got a bang on the head" [syn:
         {bash}, {bang}, {smash}, {belt}]
     4: a bad experience; "the school of hard knocks"
     5: the act of hitting vigorously; "he gave the table a whack"
        [syn: {belt}, {rap}, {whack}, {whang}]
     v 1: deliver a sharp blow or push :"He knocked the glass clear
          across the room" [syn: {strike hard}]
     2: rap with the knuckles; "knock on the door"
     3: knock against with force or violence; "My car bumped into
        the tree" [syn: {bump}]
     4: make light, repeated taps on a surface; "he was tapping his
        fingers on the table impatiently" [syn: {tap}, {rap}, {pink}]
     5: sound like a car engine that is firing too early; "the car
        pinged when I put in low-octane gasoline"; "The car pinked
        when the ignition was too far retarded" [syn: {pink}, {ping}]
     6: find fault with; express criticism of; point out real or
        perceived flaws; "The paper criticized the new movie";
        "Don't knock the food--it's free" [syn: {criticize}, {criticise},
         {pick apart}] [ant: {praise}]
Source: WordNet® 2.0