defend vs rationalise

defend and rationalise both are verbs.

Word	Noun	Adjective	Verb	Adverb
defend	No	No	Yes	No
rationalise	No	No	Yes	No

As verbs, rationalise is a hyponym of defend; that is, rationalise is a word with a more specific, narrower meaning than defend:

defend (verb)	rationalise (verb)
argue or speak in defense of	weed out unwanted or unnecessary things
state or assert	remove irrational quantities from
be on the defensive; act against an attack	think rationally; employ logic or reason
protect against a challenge or attack	defend, explain, clear away, or make excuses for by reasoning
protect or fight for as a champion	structure and run according to rational or scientific principles in order to achieve desired results
fight against or resist strongly
be the defense counsel for someone in a trial