overturn vs knock over

overturn is a noun but knock over is not a noun.

Word	Noun	Adjective	Verb	Adverb
overturn	Yes	No	Yes	No
knock over	No	No	Yes	No

As verbs, overturn and knock over are synonyms defined as:

overturn and knock over: cause to overturn from an upright or normal position

Other synonyms of overturn include bowl over, tip over, tump over, turn over, upset.

overturn (noun)	knock over (noun)
the act of upsetting something
an improbable and unexpected victory

overturn (verb)	knock over (verb)
change radically	cause to overturn from an upright or normal position
rule against
cancel officially
turn from an upright or normal position
cause to overturn from an upright or normal position
cause the downfall of; of rulers