sixer vs half a dozen

sixer and half a dozen both are nouns.

Word	Noun	Adjective	Verb	Adverb
sixer	Yes	No	No	No
half a dozen	Yes	No	No	No

As nouns, sixer and half a dozen are synonyms defined as:

sixer and half a dozen: the cardinal number that is the sum of five and one

Other synonyms of sixer include 6, Captain Hicks, hexad, sestet, sextet, sextuplet, sise, six, VI.

sixer (noun)	half a dozen (noun)
the cardinal number that is the sum of five and one	the cardinal number that is the sum of five and one