mask vs block out

mask is a noun but block out is not a noun.

Word	Noun	Adjective	Verb	Adverb
mask	Yes	No	Yes	No
block out	No	No	Yes	No

As verbs, mask and block out are synonyms defined as:

mask (noun)	block out (noun)
activity that tries to conceal something
a covering to disguise or conceal the face
a protective covering worn over the face
a party of guests wearing costumes and masks

mask (verb)	block out (verb)
put a mask on or cover with a mask	plan where and when songs should be inserted into a theatrical production, or plan a theatrical production in general
shield from light	indicate roughly
cover with a sauce	shield from light
hide under a false appearance	prevent from entering
make unrecognizable