bottle up vs stifle

bottle up is not a noun while stifle is a noun.

Word	Noun	Adjective	Verb	Adverb
bottle up	No	No	Yes	No
stifle	Yes	No	Yes	No

As verbs, stifle is a hyponym of bottle up; that is, stifle is a word with a more specific, narrower meaning than bottle up:

bottle up: consciously restrain from showing; of emotions, desires, impulses, or behavior
stifle: suppress or constrain so as to lessen in intensity

Other hyponyms of bottle up include dampen, muffle, repress, smother, strangle, choke.

bottle up (noun)	stifle (noun)
	joint between the femur and tibia in a quadruped; corresponds to the human knee

bottle up (verb)	stifle (verb)
consciously restrain from showing; of emotions, desires, impulses, or behavior	suppress or constrain so as to lessen in intensity
	be asphyxiated; die from lack of oxygen
	suppress in order to conceal or hide
	impair the respiration of or obstruct the air passage of