initial
US /ɪˈnɪʃ.əl/
UK /ɪˈnɪʃ.əl/

1.
inicial
the first letter of a name or word, typically a person's first name or a significant word in a phrase.
:
•
Please write your initials at the bottom of the form.
Por favor, escreva suas iniciais na parte inferior do formulário.
•
Her necklace had her boyfriend's initial on it.
O colar dela tinha a inicial do namorado.
1.
rubricar, assinar com iniciais
mark (a document) with one's initials, typically as a sign of approval or to indicate that one has read it.
:
•
Please initial each page of the contract.
Por favor, rubrique cada página do contrato.
•
She initialed the changes to confirm her approval.
Ela rubricou as alterações para confirmar sua aprovação.