We don't have synonyms for sign-board yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are sign, sin and sigh.
(n) :
(countable, uncountable) A visible fact that shows that something exists or may happen.
(n) :
A mark or another symbol used to represent something.
(n) :
A clearly visible object, generally flat, bearing a short message in words or pictures.
(n) :
(Canada, US, Australia, uncountable) Physical evidence left by an animal.
(n) :
A specific gesture or motion used to communicate by those with speaking or hearing difficulties; now specifically, a linguistic unit in sign language equivalent to word in spoken languages.
(n) :
(countable, uncountable) A visible fact that shows that something exists or may happen.
(n) :
A mark or another symbol used to represent something.
(n) :
A clearly visible object, generally flat, bearing a short message in words or pictures.
(n) :
(Canada, US, Australia, uncountable) Physical evidence left by an animal.
(n) :
A specific gesture or motion used to communicate by those with speaking or hearing difficulties; now specifically, a linguistic unit in sign language equivalent to word in spoken languages.