isotonic (Adjective) — (used of solutions) having the same or equal osmotic pressure.
isotonic (Adjective) — Relating to or characterized by the equal intervals of a musical scale. ex. "isotonic tuning"
isotonic (Adjective) — (physiology) of or involving muscular contraction in which tension is constant while length changes.
isotonic (Adjective) — (physiology) of two or more muscles; having equal tension.