• to put sy on guard, to put sy on sy's guard
• to read the riot act to sy
• admonitory, exhortative, exhortatory, premonitory, token, warning
• admonishment, admonition, caution, cue, exhortation, expostulation, indication, notice, pointer, reminder, tip, warning
• caution board, danger board
• he gave a cough to warn me
• my warning had the desired effect
• my warning had the desired effect
• to be warned in confidence
• he gave a cough to warn me