Definitions of singular:

• noun:   the form of a word that is used to denote a singleton
• adjective:   grammatical number category referring to a single item or unit
• adjective:   the single one of its kind

  Example: "A singular example"

• adjective:   being a single and separate person or thing

  Example: "Can the singular person be understood apart from his culture?"

• adjective:   unusual or striking

  Example: "Such poise is singular in one so young"

• adjective:   beyond or deviating from the usual or expected

  Example: "Singular behavior"