1.(used of solutions) having the same or equal osmotic pressure (Freq. 3) • Syn: isosmotic • Ant: hypertonic, hypotonic 2. relating to or characterized by the equal intervals of a musical scale (Freq. 1) - isotonic tuning • Pertains to noun: tone 3. of or involving muscular contraction in which tension is constant while length changes • Ant: isometric • Topics: physiology 4. of two or more muscles; having equal tension • Similar to: tense • Topics: physiology