1 : a long, thin mark that is a different color from its background
He left streaks where he wiped the glass.
The miners had streaks of coal dust on their faces.
2 : a quality that is noticeable especially because it is different from a person's other qualities — usually singular
a streak of stubbornness = a stubborn streak
She has an adventurous/competitive streak in her.
He has a mean streak. [=a tendency to be mean]
3 : a period of repeated success or failure
a lucky streak
a streak of 11 straight victories
a winning/losing streak [=a series of wins/losses]
The team has recently been on a hot streak. [=the team has been winning a lot of games recently]
4 : a long, narrow area or flash of light
a streak of lightning/light