Noble Silence is a term attributed to the Buddha, for his reported responses to certain questions about reality. One such instance is when he was asked the fourteen unanswerable questions. In similar situations he often responded to antinomy-based descriptions of reality by saying that both antithetical options presented to him were inappropriate.
This does not indicate misology or disdain for philosophy on the Buddha's part. Rather, it indicates that he viewed these questions as not leading to true knowledge. Dependent origination is one of the Buddha's great contributions to philosophy, and provides a framework for analysis of reality that is not based on metaphysical assumptions regarding existence or non-existence, but instead on direct cognition of phenomena as they are presented to the mind. This informs and supports the Buddhist approach to liberation via ethical and meditative training known as the Noble Eightfold Path.
Pali Canon
While silence is generally thought to be something observable on the outside of a person, an external state, whether they are talking, in the [Pali Canon] noble is an internal state which is synonymous with [jhana].
"But what is noble silence?' Then the thought occurred to me, 'There is the case where a monk, with the stilling of directed thoughts & evaluations, [1] enters & remains in the second jhāna: rapture & pleasure born of concentration, unification of awareness free from directed thought & evaluation — internal assurance. This is called noble silence.'"
Of the eight jhanas, in the second jhana is when the inner dialog goes silent during meditation.