2. Synonym: Frankly speaking.
3, antonym: ulterior motives.
4. Idiom usage: combination; As predicate, attribute and adverbial; With praise.
5, idiom source:
(1) Notes to the Book of Jin: "When a gentleman walks, when _ (thunder) falls, it is like the sun and moon in Jiao Ran."
(2) Song Zhuxi's "Zhuzi Language" Volume 74: "For example, an aboveboard person is a good person, and an ignorant person is not a good person."