  Millisecond pulsars (MSP) are an important subclass of rotation powered
pulsars (RPP), traditionally defined as those with $P_s < 20-30$~ms and $B_s
\lesssim 10^{10}$~G. We re-examine this definition by applying Gaussian mixture
model (GMM) analysis to identify distinct clusters within the RPP population
and find that the MSPs appear to be better demarcated by the condition
$\mathbf{P_s \lesssim 16}$~ms.
