A streak is a mark or characteristic. What makes you keep trying to wipe the streak of permanent marker off the white couch — your clean streak or your stubborn streak?
Like a mark or stain, a streak in a person is a characteristic or strain that runs through them — like a mean streak. The noun streak can also refer to an unbroken chain of events — you’ll want a lucky streak to keep going and a losing streak to come to a quick end. As a verb, to streak means to dash, sometimes without clothes. If you talk a blue streak, you’ve got a lot to say, very quickly.