The Collaborative International Dictionary of English v.0.48:

Anguish \An"guish\, n. [OE. anguishe, anguise, angoise, F.
   angoisse, fr. L. angustia narrowness, difficulty, distress,
   fr. angustus narrow, difficult, fr. angere to press together.
   See Anger.]
   Extreme pain, either of body or mind; excruciating distress.
   [1913 Webster]

         But they hearkened not unto Moses for anguish of
         spirit, and for cruel bondage.           --Ex. vi. 9.
   [1913 Webster]

         Anguish as of her that bringeth forth her first child.
                                                  --Jer. iv. 31.
   [1913 Webster]

   Note: Rarely used in the plural:

               Ye miserable people, you must go to God in
               anguishes, and make your prayer to him.
                                                  --Latimer.
         [1913 Webster]

   Syn: Agony; pang; torture; torment. See Agony.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Anguish \An"guish\, v. t. [Cf. F. angoisser, fr. L. angustiare.]
   To distress with extreme pain or grief. [R.] --Temple.
   [1913 Webster]

WordNet (r) 3.0 (2006):

anguish
    n 1: extreme mental distress [syn: anguish, torment,
         torture]
    2: extreme distress of body or mind
    v 1: suffer great pains or distress
    2: cause emotional anguish or make miserable; "It pains me to
       see my children not being taught well in school" [syn:
       pain, anguish, hurt]

Moby Thesaurus II by Grady Ward, 1.0:

143 Moby Thesaurus words for "anguish":
   ache, aching heart, afflict, affliction, aggrieve, agonize, agony,
   agony of mind, ail, angst, anxiety, atrocious pain, bale,
   barb the dart, bitterness, blanch, bleed, bleeding heart, blench,
   boredom, break down, bring to tears, broken heart, bruise, care,
   carking care, cheerlessness, crucifixion, crush, crushing, cut,
   cut up, depression, depth of misery, desolate, desolation, despair,
   discomfort, discomposure, discontent, dislike, displeasure,
   disquiet, dissatisfaction, distress, disturb, dole, draw tears,
   dread, dullness, embitter, emptiness, ennui, excruciation,
   existential woe, extremity, feel pain, feel the pangs, flatness,
   go hard with, grief, grieve, grimace, grimness, have a misery,
   heartache, heartbreak, heartfelt grief, heartgrief, heavy heart,
   hurt, hurt the feelings, infelicity, inquietude, inundate,
   joylessness, lack of pleasure, lamentation, languishment, malaise,
   martyrdom, martyrization, melancholia, melancholy, misery, nausea,
   nongratification, nonsatisfaction, oppress, overwhelm, pain,
   painfulness, pang, pierce, pining, pound, prick, prostrate,
   prostration, rack, regret, rue, sadness, savorlessness, shoot,
   shrink, smart, sorrow, sorrowing, spleen, stab, staleness, sting,
   suffer, suffer anguish, suffering, suicidal despair, tastelessness,
   tediousness, tedium, thrill, throb, tingle, torment, torture,
   trouble, twinge, twist the knife, twitch, uncomfortableness,
   unease, uneasiness, unhappiness, unpleasure, unsatisfaction, upset,
   vexation of spirit, wince, woe, worry, wound, wretchedness,
   writhe