GIRIDHANVA

Shiva is called as Giridhanva because he turned Mount Meru into a bow. This is the same bow which was used to destroy three cities of Tripur demon. In Sanskrit a sports-ball is also said as Giri. Here word ‘Giri’ is referred for Avidya (ignorance). Avidya is nothing but a playing game for Shiva, therefore he is Giridhanva.
At some places Giri is also meant for speech. Brahmins (Vedic priests) are also titled as Giridhanva because they attack through their tongue in the form of curse. A Brahmin who is dedicated to study of Vedas and who is engageddd in search of absolute truth, he is non-different to Shiva. Shiva himself became the sage Durvasa who is well known as anger personified, therefore he is called Giridhanva. A unique explanation by Bhaskar Roy is given here—

Eवाग्विषये त्वं मरुरिव भवसि त्वां हि मनागभिदधति न वाचो
दिव्यरथे वा पुरदहनविधौ वेदमायाः किल चतुरतुरंगः।
चक्रयुगं ते दिनरजनीकरौ वाणशरीरभृदभवदुपेन्द्रो
मेरुरभूते धनुरुरगपति र्ज्याऽभवदीश! तदसि गिरिधन्वा॥

Purport: O Lord! You are compared to a desert in relation to speech, because words are not capable to expose you, therefore you are Giridhanva. Otherwise at the time of killing of Vidyunmali, certainly the Vedas acted as the swift horses in your chariot, sun and moon acted as the wheels of chariot, Vishnu personally acted as an arrow, Meru mountain acted as bow and serpent Vasuki acted as a string of the bow, therefore you are known as Giridhanva.
Shruti tells that Shiva is beyond the power of speech— Yato vacho nivartante, naiva vacha na mansa, napi vacha. In meditational practices, the spinal cord in the human body is named as Meru-danda. The Kundalini power is raised in this cord. This spinal cord is the bow of Shiva, by which the ignorance of three bodies is destroyed.