quasiperiodic
chiefly . almost or approximately periodic.
of a function: such that increasing the variable by a certain fixed amount multiplies the value of the function by a fixed function, or increases it additively by a fixed function.
of a motion, oscillation, etc.: having two periods incommensurable in duration.
of a pattern, crystal lattice, etc.: such that any element recurs elsewhere, but at irregular intervals.
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