draining board vs drainboard

draining board and drainboard both are nouns.

Word	Noun	Adjective	Verb	Adverb
draining board	Yes	No	No	No
drainboard	Yes	No	No	No

As nouns, draining board and drainboard are synonyms defined as:

draining board and drainboard: a board beside a kitchen sink and inclined to drain into the sink

draining board (noun)	drainboard (noun)
a board beside a kitchen sink and inclined to drain into the sink	a board beside a kitchen sink and inclined to drain into the sink