The Collaborative International Dictionary of English v.0.48:

Meningitis \Men`in*gi"tis\, n. [NL. See Meninges, and
   -itis.] (Med.)
   Inflammation of the membranes of the brain or spinal cord.
   [1913 Webster]

   Cerebro-spinal meningitis. See under Cerebro-spinal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

meningitis
    n 1: infectious disease characterized by inflammation of the
         meninges (the tissues that surround the brain or spinal
         cord) usually caused by a bacterial infection; symptoms
         include headache and stiff neck and fever and nausea

Moby Thesaurus II by Grady Ward, 1.0:

255 Moby Thesaurus words for "meningitis":
   African lethargy, Asiatic cholera, Chagres fever, German measles,
   Haverhill fever, acute articular rheumatism, adenoiditis,
   adrenitis, ague, alkali disease, amebiasis, amebic dysentery,
   anthrax, appendicitis, arteritis, arthritis deformans,
   arthritis fungosa, arthritis pauperum, atrophic arthritis,
   atrophic inflammation, bacillary dysentery, bastard measles,
   black death, black fever, blackwater fever,
   blennorrhagic arthritis, brain fever, breakbone fever, bronchitis,
   brucellosis, bubonic plague, bunion, bursitis, cachectic fever,
   capillaritis, carditis, catarrh, catarrhal inflammation,
   cerebellitis, cerebral meningitis, cerebral rheumatism, cerebritis,
   cerebrospinal meningitis, chicken pox, cholera,
   chronic infectious arthritis, chronic inflammation,
   cirrhotic inflammation, climactic arthritis, clitoritis, colitis,
   collagen disease, conjunctivitis, cowpox, cystitis, dandy fever,
   deer fly fever, degenerative arthritis, dengue, dengue fever,
   diffuse inflammation, diphtheria, dumdum fever, dysentery,
   elephantiasis, encephalitis, encephalitis lethargica, endocarditis,
   enteric fever, enteritis, equine encephalomyelitis, erysipelas,
   exudative inflammation, famine fever, fibroid inflammation,
   five-day fever, flu, focal inflammation, frambesia, gastritis,
   gingivitis, glandular fever, glossitis, gonococcal arthritis,
   gonorrheal arthritis, gonorrheal rheumatism, gout, gouty arthritis,
   grippe, hansenosis, hemophilic arthritis, hepatitis, herpes,
   herpes simplex, herpes zoster, histoplasmosis, hookworm,
   hydrophobia, hyperplastic inflammation, hypertrophic arthritis,
   hypertrophic inflammation, infantile paralysis,
   infectional arthritis, infectious hepatitis,
   infectious mononucleosis, inflammation, inflammatory rheumatism,
   influenza, irritable bowel syndrome, jail fever, jungle rot,
   kala azar, kissing disease, laryngitis, lepra, leprosy,
   leptospirosis, loa loa, loaiasis, lockjaw, lumbago, madness,
   malaria, malarial fever, marsh fever, mastoiditis, measles,
   menopausal arthritis, metastatic inflammation, metritis, milk leg,
   milzbrand, mucous colitis, mumps, mumps meningitis, myelitis,
   necrotic inflammation, nephritis, neuritis,
   obliterative inflammation, ophthalitis, ophthalmia, orchitis,
   ornithosis, osseous rheumatism, osteitis, osteoarthritis,
   osteomyelitis, otitis, ovaritis, paradental pyorrhea,
   paratyphoid fever, parotitis, parrot fever, penitis, pericarditis,
   periodontitis, peritonitis, pertussis, pharyngitis, phlebitis,
   pneumonia, podagra, polio, poliomyelitis, polyarthritis rheumatism,
   ponos, proliferative arthritis, prostatitis, psittacosis,
   pyonephritis, pyorrhea, pyorrhea alveolaris, rabbit fever, rabies,
   rat-bite fever, reactive inflammation, relapsing fever,
   rheumatic fever, rheumatism, rheumatiz, rheumatoid arthritis,
   rhinitis, rickettsialpox, ringworm, rubella, rubeola, scarlatina,
   scarlet fever, schistosomiasis, sclerosing inflammation,
   septic sore throat, seroplastic inflammation, serous inflammation,
   serum hepatitis, shingles, simple inflammation, sinusitis,
   sleeping sickness, sleepy sickness, smallpox, snail fever,
   spastic colon, specific inflammation, splenic fever, spotted fever,
   strep throat, subacute rheumatism, suppurative arthritis,
   suppurative inflammation, swamp fever, syphilitic arthritis,
   tennis elbow, testitis, tetanus, thrombophlebitis, thrush, tinea,
   tonsilitis, torticollis, toxic inflammation,
   traumatic inflammation, trench fever, trench mouth, tuberculosis,
   tuberculous arthritis, tuberculous rheumatism, tularemia, typhoid,
   typhoid fever, typhus, typhus fever, ulcerative colitis,
   undulant fever, uratic arthritis, ureteritis, urethral arthritis,
   urethritis, uteritis, vaccinia, vaginitis, varicella, variola,
   venereal disease, vertebral arthritis, viral dysentery,
   visceral rheumatism, vulvitis, whooping cough, wryneck, yaws,
   yellow fever, yellow jack, zona, zoster