From non- + secular. <span class="searchmatch">nonsecular</span> (not comparable) Not secular; religious. (atomic physics) Perturbed over time. 2000, S. A. Dikanov, Two-dimensional ESEEM...
Analytical Chemistry (Atta-ur-Rahman, ed.), page 539 The secular A and <span class="searchmatch">nonsecular</span> B parts of hyperfine interaction for any particular frequencies να and...