old vs smashing

old and smashing both are nouns.

Word	Noun	Adjective	Verb	Adverb
old	Yes	Yes	No	No
smashing	Yes	Yes	No	No

As adjectives, old and smashing are synonyms defined as:

Other synonyms of old include bang-up, bully, corking, cracking, dandy, great, groovy, keen, neat, nifty, not bad, peachy, slap-up, swell.

old (noun)	smashing (noun)
past times	the act of breaking something into small pieces

old (adjective)	smashing (adjective)
of long duration; not new	excellent
(used especially of persons) having lived for a relatively long time or attained a specific age
skilled through long experience
(used for emphasis) very familiar
excellent
just preceding something else in time or order
belonging to some prior time