The Collaborative International Dictionary of English v.0.48:

Appel \Ap`pel"\, n. [F., prop., a call. See Appeal, n.]
   (Fencing)
   A tap or stamp of the foot as a warning of intent to attack;
   -- called also attack.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Attack \At*tack"\, v. t. [imp. & p. p. Attacked; p. pr. & vb.
   n. Attacking.] [F. attaquer, orig. another form of attacher
   to attack: cf. It. attacare to fasten, attack. See Attach,
   Tack a small nail.]
   1. To fall upon with force; to assail, as with force and
      arms; to assault. "Attack their lines." --Dryden.
      [1913 Webster]

   2. To assail with unfriendly speech or writing; to begin a
      controversy with; to attempt to overthrow or bring into
      disrepute, by criticism or satire; to censure; as, to
      attack a man, or his opinions, in a pamphlet.
      [1913 Webster]

   3. To set to work upon, as upon a task or problem, or some
      object of labor or investigation.
      [1913 Webster]

   4. To begin to affect; to begin to act upon, injuriously or
      destructively; to begin to decompose or waste.
      [1913 Webster]

            On the fourth of March he was attacked by fever.
                                                  --Macaulay.
      [1913 Webster]

            Hydrofluoric acid . . . attacks the glass. --B.
                                                  Stewart.
      [1913 Webster]

   Syn: To Attack, Assail, Assault, Invade.

   Usage: These words all denote a violent onset; attack being
          the generic term, and the others specific forms of
          attack. To attack is to commence the onset; to assail
          is to make a sudden and violent attack, or to make
          repeated attacks; to assault (literally, to leap upon)
          is to attack physically by a had-to-hand approach or
          by unlawful and insulting violence; to invade is to
          enter by force on what belongs to another. Thus, a
          person may attack by offering violence of any kind; he
          may assail by means of missile weapons; he may assault
          by direct personal violence; a king may invade by
          marching an army into a country. Figuratively, we may
          say, men attack with argument or satire; they assail
          with abuse or reproaches; they may be assaulted by
          severe temptations; the rights of the people may be
          invaded by the encroachments of the crown.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Attack \At*tack"\, v. i.
   To make an onset or attack.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Attack \At*tack"\, n. [Cf. F. attaque.]
   1. The act of attacking, or falling on with force or
      violence; an onset; an assault; -- opposed to defense.
      [1913 Webster]

   2. An assault upon one's feelings or reputation with
      unfriendly or bitter words.
      [1913 Webster]

   3. A setting to work upon some task, etc.
      [1913 Webster]

   4. An access of disease; a fit of sickness.
      [1913 Webster]

   5. The beginning of corrosive, decomposing, or destructive
      action, by a chemical agent.
      [1913 Webster]

WordNet (r) 3.0 (2006):

attack
    n 1: (military) an offensive against an enemy (using weapons);
         "the attack began at dawn" [syn: attack, onslaught,
         onset, onrush]
    2: an offensive move in a sport or game; "they won the game with
       a 10-hit attack in the 9th inning"
    3: intense adverse criticism; "Clinton directed his fire at the
       Republican Party"; "the government has come under attack";
       "don't give me any flak" [syn: fire, attack, flak,
       flack, blast]
    4: ideas or actions intended to deal with a problem or
       situation; "his approach to every problem is to draw up a
       list of pros and cons"; "an attack on inflation"; "his plan
       of attack was misguided" [syn: approach, attack, plan of
       attack]
    5: the act of attacking; "attacks on women increased last year";
       "they made an attempt on his life" [syn: attack, attempt]
    6: a decisive manner of beginning a musical tone or phrase [syn:
       attack, tone-beginning]
    7: a sudden occurrence of an uncontrollable condition; "an
       attack of diarrhea"
    8: the onset of a corrosive or destructive process (as by a
       chemical agent); "the film was sensitive to attack by acids";
       "open to attack by the elements"
    9: strong criticism; "he published an unexpected attack on my
       work"
    v 1: launch an attack or assault on; begin hostilities or start
         warfare with; "Hitler attacked Poland on September 1, 1939
         and started World War II"; "Serbian forces assailed Bosnian
         towns all week" [syn: attack, assail] [ant: defend]
    2: attack in speech or writing; "The editors of the left-leaning
       paper attacked the new House Speaker" [syn: attack,
       round, assail, lash out, snipe, assault]
    3: take the initiative and go on the offensive; "The Serbs
       attacked the village at night"; "The visiting team started to
       attack" [syn: attack, aggress]
    4: attack someone physically or emotionally; "The mugger
       assaulted the woman"; "Nightmares assailed him regularly"
       [syn: assail, assault, set on, attack]
    5: set to work upon; turn one's energies vigorously to a task;
       "I attacked the problem as soon as I got out of bed"
    6: begin to injure; "The cancer cells are attacking his liver";
       "Rust is attacking the metal"

Moby Thesaurus II by Grady Ward, 1.0:

483 Moby Thesaurus words for "attack":
   Jacksonian epilepsy, MO, Rolandic epilepsy, abdominal epilepsy,
   abuse, accept, access, acquired epilepsy, action,
   activated epilepsy, activation, affect, affect epilepsy, affection,
   aggression, aggressiveness, ailment, akinetic epilepsy, algorithm,
   all-out war, ambush, amok, apoplexy, appeal to arms, approach,
   armed combat, armed conflict, arrangement, arrest, articulation,
   assail, assailing, assailment, assault, assume, attack, attempt,
   autonomic epilepsy, barbarize, batter, battering, battle, begin,
   beleaguer, bellicosity, belligerence, belligerency, berate,
   berating, beset, besiege, bitter words, blackening, blister, blitz,
   blockade, blockage, bloodshed, blueprint, blueprinting, bout,
   brutalize, buckle down, buckle to, burn, bushwhack, butcher,
   butchery, calculation, cardiac epilepsy, carry on, castigate,
   censure, challenge, charge, charting, chauvinism, citation,
   clonic spasm, clonus, combat, combativeness, come at, come down on,
   complaint, conception, condemn, contrivance, contumely, convulsion,
   corrode, corrosion, cortical epilepsy, course, crack down on,
   cramp, criminate, criticism, criticize, cry out against,
   cry out on, cry shame upon, cursive epilepsy, declare war,
   decompose, decrial, decry, defy, delivery, denigrate, denigration,
   denounce, denunciation, deprecate, deprecation, descend on,
   descend upon, descent, design, destroy, destruction, device,
   devour, diatribe, disease, disorder, disorderliness, disparage,
   disparagement, disposition, dissolve, diurnal epilepsy, dive into,
   draw first blood, drive, eat, eclampsia, embark in, embark upon,
   encompass, endeavor, engage in, engage in battle, enter on,
   enter upon, enterprise, enunciation, envisagement, epilepsia,
   epilepsia gravior, epilepsia major, epilepsia minor,
   epilepsia mitior, epilepsia nutans, epilepsia tarda, epilepsy,
   epitasis, erode, erosion, excoriate, execration, fall, fall into,
   fall on, fall to, fall upon, falling sickness, fashion, fay, fever,
   fight, fighting, figuring, fit, focal epilepsy, foray,
   forcible seizure, foresight, forethought, form, frenzy, furor,
   fury, fustigate, game, gang up on, get busy, get cracking,
   get going, get under way, get with it, go about, go at, go for,
   go in for, go into, go on, go to it, go upon, grand mal, graphing,
   grip, ground plan, guidelines, guise, hammer, harass, hard words,
   harry, haute mal, have at, hit, hit like lightning, hop to it,
   hostilities, hot war, hysterical epilepsy, ictus, idea, implicate,
   implication, impugn, impugnment, incriminate, incrimination,
   inculpate, inculpation, incursion, infect, inroad, intention,
   invade, invasion, invective, inveigh against, invest, involve,
   involvement, irrupt, jawing, jeremiad, jingoism, jump, jump to it,
   killing, la guerre, land on, larval epilepsy, laryngeal epilepsy,
   laryngospasm, lash, latent epilepsy, launch forth, launch into,
   lay about, lay about one, lay at, lay hands on, lay into, lay on,
   lay waste, laying waste, layout, levy war on, light into, line,
   line of action, lines, lineup, lockjaw, long-range plan, loot,
   looting, make war on, malign, manner, manner of working, mapping,
   massacre, master plan, matutinal epilepsy, maul, means,
   menstrual epilepsy, method, methodology, might of arms,
   militarization, military operations, mobilization, mode,
   mode of operation, mode of procedure, modus operandi, move into,
   mug, murderous insanity, musicogenic epilepsy, muster,
   myoclonous epilepsy, nocturnal epilepsy, obstreperousness,
   occlusion, offense, offensive, onset, onslaught, open hostilities,
   open war, operations research, order, organization, orgasm,
   outbreak, paroxysm, petit mal, philippic, phonation,
   physiologic epilepsy, pillage, pillaging, pitch in, pitch into,
   plan, planning, planning function, plunge into, pounce upon, pound,
   practice, prearrangement, press, procedure, proceed to, proceeding,
   process, program, program of action, pronunciation,
   psychic epilepsy, psychokinesia, psychomotor epilepsy, pugnacity,
   push, rage, raid, ramp, rampage, rant, rape, rating,
   rationalization, rave, reflex epilepsy, resort to arms, revile,
   revilement, riot, rioting, roar, roast, rotatoria, routine, ruin,
   rush, sack, sacking, sail into, sally, savage, scarify, scathe,
   schedule, schema, schematism, schematization, scheme,
   scheme of arrangement, scorch, screed, seize, seizure,
   sensory epilepsy, serial epilepsy, set about, set at, set forward,
   set going, set on, set to, set to work, set upon, setup,
   sexual climax, shooting war, siege, skin alive, slash, slaughter,
   sortie, sow chaos, sowing with salt, spasm, spell, square up,
   start, start in, state of war, stoppage, storm, strategic plan,
   strategy, strike, strike at, stroke, style, surprise,
   swoop down on, system, systematization, tack, tackle,
   tactical plan, tactics, take on, take the offensive, take up,
   tardy epilepsy, tear, tear around, technique, terrorize, tetanus,
   tetany, the big picture, the drill, the how, the picture,
   the sword, the way of, throes, thromboembolism, thrombosis, tirade,
   tone, tongue-lashing, tonic epilepsy, tonic spasm, torsion spasm,
   total war, traumatic epilepsy, trismus, trounce, turn, turn on,
   turn to, ucinate epilepsy, undertake, unruliness, utterance,
   vandalize, venture upon, vilification, vilify, violate, violation,
   visitation, vituperation, vocalization, voicing, wade into, war,
   warfare, warmaking, warmongering, warring, wartime, waste, wasting,
   way, wise, working plan, wreck