B1
the first letter of a name, especially when used to represent a name
Dictionary examples:
Lucy's initials 'L.O.L.' always made her new friends laugh out loud. (0.0)
The chef's initials 'E.G.G.' were perfect for his famous breakfast restaurant. (0.0)
Bob's initials 'B.A.D.' made him feel like a cool bad boy. (0.0)
They carved their initials into a tree. (47.6)
He wrote his initials, P.M.R., at the bottom of the page. (56.1)
Paul M. Reynolds refused to say what the initial "M" stood for. (62.5)