a member of an organization of boys (Boy Scouts) founded in England in 1908 by Lieut. Gen. Sir Robert S. S. Baden-Powell, that seeks to develop certain skills in its members, as well as character, self-reliance, and usefulness to others.
(lowercase) a member of any similar society elsewhere.
(lowercase) Sometimes Disparaging. a person whose deeds, obliging personality, idealism, etc., exceed normal expectations.
Use of boy scout to mean ‘someone who is obliging and idealistic’ usually implies that the person is naive or unworldly.