про́седь

rare #38516nounfeminineuncountablenoun in -ь

1.
streak of grey (in the hair), grey streaks, greying hair
У неё тёмные во́лосы с про́седью.
She has dark hair streaked with grey.
Usually of hair that is only partly grey; often in the phrase «волосы с проседью».

Examples

С годами проседь всё сильнее проступала в волосах.
Over the years, the gray in his hair became increasingly noticeable.
Проседь на висках делала его старше.
The gray at his temples made him look older.
В его волосах появилась заметная проседь.
A noticeable streak of gray appeared in his hair.