senior sibling
nounUK /ˈsiː.ni.ə ˈsɪb.lɪŋ/
US /ˈsiː.njɚ ˈsɪb.lɪŋ/
An older brother or sister in your family.
My senior sibling helps me with my homework every day.
RELATED WORDS
OTHER MEANINGS
2. A sibling who is older than you by birth order.
As the senior sibling, she always sat in the front seat of the car.
3. An older sibling who acts as a role model or guide.
His senior sibling taught him how to ride a bike.
4. The firstborn or eldest child among siblings.
The senior sibling in their family is now in college.