a. Bot. [f. TRANS- 5 + L. apex, apic-em, APEX: see APICAL.] Transverse to the apical axis (of a diatom).
1900. B. D. Jackson, Gloss. Bot. Terms, 273. Transapical,… at right angles to the apical axis, passing through the centre of the pervalvar (main longitudinal) axis of a Diatom; transapical Plane, the plane at right angles to both valvar and apical planes, passing through the pervalvar and transapical axis (O. Mueller).
