a coloured line, especially one that is not straight or has been made accidentally:
Sue has blonde streaks in her hair.
a part of someone's character that is different from the rest of their character:
a mean streak
His serious nature was lightened by a streak of mischief.
a period of time during which you continue to be successful or to fail
be on a winning/losing streak
Celtic are on a six-game winning streak.
a long straight flash of lightning, fire etc