Definition of tunica in US English:



  • 1Anatomy
    A membranous sheath enveloping or lining an organ.

    with Latin modifier ‘tunica media’
    • ‘Muscle fibers arranged in various striae form the tunica media of veins, for example, in medium-sized vessels.’
    • ‘Veins typically have 3 layers: tunica intima, media, and adventitia.’
    • ‘Arterial calcification most commonly involves the tunica media.’
    • ‘The tumor completely encased the right coronary artery with external compression of the vessel wall without invasion into the tunica media.’
    • ‘The tumor seemed to infiltrate the tunica albuginea and the rete testis, as well as the root of the epididymis.’
    covering, cover, case, casing, envelope, sleeve, wrapper
    View synonyms
  • 2Botany
    The outer layer or layers of cells in an apical meristem, which contribute to surface growth.


Late 17th century: from Latin, literally ‘tunic’.