Sri Matre Namaha
Niḥsaṃśayā – The One Hundred & Seventy Second name in Lalitha Sahasranamam.
nirgatah samsayah yasyah sa
She who is without doubt
Niḥsaṃśayā : Nis means nothing / nil and samsaya means doubt;
This quality (i.e., being without doubt) of guru is described here and the latter is described in the name that follows.
Doubts arise while seeking knowledge. When She herself is the knowledge, where is the question of doubts for Her?
She is Sarva Gnanamayi and Sarva Shaktimayi hence, there is no groom for any doubts for her.