1. to tell someone about a possible danger, problem, or other unpleasant thing that might happen
2. to tell someone that they will be punished if they continue to behave badly

Examples

• The weather service warned of severe storms approaching.
• I warned him not to touch the hot stove.
• She warned me about the icy roads this morning.
• The teacher warned the students to stop talking during the test.
• Police warned drivers to avoid the flooded highway.
• His mother warned him that he would lose his privileges if he didn’t clean his room.
• The sign warns visitors about dangerous wildlife in the area.