overflow vs overspill

overflow and overspill both are nouns.

Word	Noun	Adjective	Verb	Adverb
overflow	Yes	No	Yes	No
overspill	Yes	No	No	No

As nouns, overflow and overspill are synonyms defined as:

overflow and overspill: the occurrence of surplus liquid (as water) exceeding the limit or capacity

Other synonyms of overflow include runoff.

overflow (noun)	overspill (noun)
a large flow	the occurrence of surplus liquid (as water) exceeding the limit or capacity
the occurrence of surplus liquid (as water) exceeding the limit or capacity	the relocation of people from overcrowded cities; they are accommodated in new houses or apartments in smaller towns

overflow (verb)	overspill (verb)
overflow with a certain feeling
flow or run over (a limit or brim)