Definition of "fissile"

This Cryſtal is a pellucid fiſſile Stone, clear as Water or Cryſtal of the Rock, and without Colour; enduring a red Heat without loſing its tranſparency, and in a very ſtrong Heat calcining without Fuſion.

a. 1728 (date written), Isaac Newton, “, published 1730, page 329

North Korea may soon have access to regular amounts of fissile material if it doesn't already ...

2014 March 30, Choe Sang-hun, “North Korea vows to use 'new form' of nuclear test”, in The New York Times‎