The Collaborative International Dictionary of English v.0.48:

Nasal \Na"sal\ (n[=a]"zal), a. [F., from L. nasus the nose. See
   Nose.]
   1. (Anat.) Of or pertaining to the nose.
      [1913 Webster]

   2. (Phon.) Having a quality imparted by means of the nose;
      and specifically, made by lowering the soft palate, in
      some cases with closure of the oral passage, the voice
      thus issuing (wholly or partially) through the nose, as in
      the consonants m, n, ng (see Guide to Pronunciation,
      [sect][sect] 20, 208); characterized by resonance in the
      nasal passage; as, a nasal vowel; a nasal utterance.
      [1913 Webster]

   Nasal bones (Anat.), two bones of the skull, in front of
      the frontals.

   Nasal index (Anat.), in the skull, the ratio of the
      transverse breadth of the anterior nasal aperture to the
      height from the base of the aperture to the nasion, which
      latter distance is taken as the standard, equal to 100.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nasal \Na"sal\, n.
   1. An elementary sound which is uttered through the nose, or
      through both the nose and the mouth simultaneously.
      [1913 Webster]

   2. (Med.) A medicine that operates through the nose; an
      errhine. [Archaic]
      [1913 Webster]

   3. (Anc. Armor) Part of a helmet projecting to protect the
      nose; a nose guard.
      [1913 Webster]

   4. (Anat.) One of the nasal bones.
      [1913 Webster]

   5. (Zool.) A plate, or scale, on the nose of a fish, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

nasal
    adj 1: of or in or relating to the nose; "nasal passages" [syn:
           rhinal, nasal]
    2: sounding as if the nose were pinched; "a whining nasal voice"
       [syn: adenoidal, pinched, nasal]
    n 1: a consonant produced through the nose with the mouth closed
         [syn: nasal consonant, nasal]
    2: an elongated rectangular bone that forms the bridge of the
       nose [syn: nasal, nasal bone, os nasale]

Moby Thesaurus II by Grady Ward, 1.0:

174 Moby Thesaurus words for "nasal":
   accented, allophone, alveolar, apical, apico-alveolar,
   apico-dental, articulated, articulation, aspiration, assimilated,
   assimilation, asthmatic, back, barytone, bilabial, blurred,
   breathing, breathy, broad, cacuminal, central, cerebral, check,
   checked, choked, choking, close, consonant, consonantal,
   continuant, croaking, dental, diphthong, dissimilated,
   dissimilation, dorsal, drawling, drawly, dysphonic,
   epenthetic vowel, errhine, expiratory, explosive, flat, front,
   glide, glossal, glottal, glottalization, guttural, hard, harsh,
   hawking, heaving, heavy, high, hoarse, huffing, inarticulate,
   indistinct, inspiratory, intonated, labial, labialization,
   labiodental, labiovelar, laryngeal, lateral, lax, light, lingual,
   liquid, lisping, low, manner of articulation, mid, mispronounced,
   modification, monophthong, monophthongal, morphophoneme, mute,
   muted, muzzy, narrow, nasalized, occlusive, open, oxytone, palatal,
   palatalized, panting, parasitic vowel, peak, pharyngeal,
   pharyngealization, pharyngealized, phone, phoneme, phonemic,
   phonetic, phonic, pitch, pitched, plosive, pneumonic, posttonic,
   prothetic vowel, puffing, pulmonary, pulmonic, quavering,
   respiratory, retroflex, rhinal, rounded, segmental phoneme,
   semivowel, shaking, shaky, sneezy, sniffling, sniffly, sniffy,
   snoring, snorting, snuffling, snuffly, snuffy, soft, sonant,
   sonority, speech sound, sternutatory, stertorous, stifled, stop,
   stopped, strangled, stressed, strong, surd, syllabic,
   syllabic nucleus, syllabic peak, syllable, tense, thick, throaty,
   tonal, tonic, transition sound, tremulous, triphthong, twangy,
   unaccented, unrounded, unstressed, velar, vocable, vocalic, vocoid,
   voice, voiced, voiced sound, voiceless, voiceless sound, voicing,
   vowel, vowellike, weak, wheezing, wheezy, wide