1. past tense of signal; to communicate or indicate something using a gesture, sound, or other sign
2. past tense of signal; to be a sign or indication of something

Examples

• The driver signaled before turning left.
• She signaled for help by waving her arms.
• The referee signaled the end of the game.
• Dark clouds signaled an approaching storm.
• The bell signaled the start of class.
• He signaled his approval with a thumbs up.
• The company’s losses signaled financial trouble.