IPA: /ˌɪndɪˈskraɪbəbli/
KK: /ɪnˈdɛskrɪbəbli/
In a way that cannot be described or expressed in words.
The beauty of the sunset was indescribably stunning.
Indescribably is formed from "in-" (meaning not), "describere" (meaning to write down or describe), and "-ably" (meaning in a manner). The word means in a manner that cannot be described or expressed.
Think of 'not' ('in-') being able to 'write down' ('describere') something — that's why indescribably means something that cannot be expressed.