preempt vs supersede

preempt is a noun but supersede is not a noun.

Word	Noun	Adjective	Verb	Adverb
preempt	Yes	No	Yes	No
supersede	No	No	Yes	No

As verbs, supersede is a hypernym of preempt; that is, supersede is a word with a broader meaning than preempt:

Other hypernyms of preempt include replace, supervene upon, supplant.

preempt (noun)	supersede (noun)
a high bid that is intended to prevent the opposing players from bidding

preempt (verb)	supersede (verb)
acquire for oneself before others can do so	take the place or move into the position of
make a preemptive bid in the game of bridge
gain possession of by prior right or opportunity, especially so as to obtain the right to buy (land)
take the place of or have precedence over