adverb, adverb taking the 'to' particle
in a whisper; in a low voice; in undertones
Describes speaking quietly so as not to be overheard; often used with 話す or 言う.
二人は隅でひそひそ話していた。
The two were whispering in the corner.
彼女は私の耳元でひそひそと秘密を教えてくれた。
She whispered the secret in my ear.
The two of them were talking in whispers in the corner.
She conveyed something in a hushed voice.
The students were quietly discussing something behind the teacher's back.