1) Intermittence 2) Irregularity 3) Unregularity 1) Intermittence 
In dynamical systems, intermittency is the irregular alternation of phases of apparently periodic and chaotic dynamics (Pomeau–Manneville dynamics), or different forms of chaotic dynamics (crisis-induced intermittency). Pomeau and Manneville described three routes to intermittency where a nearly periodic system show irregularly spaced bursts of ...
When a non-linear dynamical system alternates between periodic and chaotic behavior. See: Chaos, Dynamical Systems.