The Collaborative International Dictionary of English v.0.48:

hypertension \hypertension\ n.
   abnormally high blood pressure; especially, the chronic
   condition associated with persistent high blood pressure.
   [PJC]

WordNet (r) 3.0 (2006):

hypertension
    n 1: a common disorder in which blood pressure remains
         abnormally high (a reading of 140/90 mm Hg or greater)
         [syn: high blood pressure, hypertension] [ant:
         hypotension]

Moby Thesaurus II by Grady Ward, 1.0:

140 Moby Thesaurus words for "hypertension":
   abscess, ague, anemia, angina, angina pectoris, ankylosis, anoxia,
   aortic insufficiency, aortic stenosis, apnea, apoplectic stroke,
   apoplexy, arrhythmia, arteriosclerosis, asphyxiation, asthma,
   ataxia, atherosclerosis, atrial fibrillation, atrophy,
   auricular fibrillation, backache, beriberi heart, bleeding,
   blennorhea, cachexia, cachexy, cardiac arrest,
   cardiac insufficiency, cardiac shock, cardiac stenosis,
   cardiac thrombosis, carditis, chill, chills, colic,
   congenital heart disease, constipation, convulsion, cor biloculare,
   cor juvenum, cor triatriatum, coronary, coronary insufficiency,
   coronary thrombosis, coughing, cyanosis, diarrhea,
   diastolic hypertension, dizziness, dropsy, dysentery, dyspepsia,
   dyspnea, edema, emaciation, encased heart, endocarditis,
   extrasystole, fainting, fatigue, fatty heart, fever, fibrillation,
   fibroid heart, flask-shaped heart, flux, frosted heart, growth,
   hairy heart, heart attack, heart block, heart condition,
   heart disease, heart failure, hemorrhage, high blood pressure,
   hydrops, hypertensive heart disease, hypotension, icterus,
   indigestion, inflammation, insomnia, ischemic heart disease,
   itching, jaundice, labored breathing, low blood pressure, lumbago,
   marasmus, mitral insufficiency, mitral stenosis,
   myocardial infarction, myocardial insufficiency, myocarditis,
   myovascular insufficiency, nasal discharge, nausea, necrosis,
   ox heart, pain, palpitation, paralysis, paralytic stroke,
   paroxysmal tachycardia, pericarditis, pile, premature beat,
   pruritus, pseudoaortic insufficiency, pulmonary insufficiency,
   pulmonary stenosis, rash, rheum, rheumatic heart disease,
   round heart, sclerosis, seizure, shock, skin eruption, sneezing,
   sore, spasm, stony heart, stroke, tabes, tachycardia, thrombosis,
   tricuspid insufficiency, tricuspid stenosis, tumor, turtle heart,
   upset stomach, varicose veins, varix, ventricular fibrillation,
   vertigo, vomiting, wasting