(adjective) (1) Wearing a garment that is tightly laced up; (2) excessively conservative in opinion and behavior, very prudish, priggish.  (conservador, “certinho”)

This word has been misspelled "straight-laced" for so long that this spelling is now accepted everywhere. The adverb, though rarely used, is "straitlacedly" while the noun is "straitlacedness" (with or without the hyphen).

"My sister is so strait-laced she won't let her teenage sons eat Lady Godiva chocolates."
"Her straitlaced husband won't even go out on the beach without a tie and jacket."
"I work in a straitlaced office where the men's cubicles are on one side of the building and the women's are on the other."
Source: YourDictionary