What is the meaning of विष्णु?

Vishnu (the preserver in the Trimurti and the principal deity of Vaishnavism)

a male given name, Vishnu, from Sanskrit

Vishnu

the name of the month चैत्र (caitra) (VarBṛS.)

(with प्राजापत्य (prājāpatya)) the name of the author of RV. X, 84

the name of a son of Manu Sāvarṇa and Manu Bhautya (MārkP.)

the name of the writer of a law-book

the name of the father of the 11th अर्हत् (arhat) of the present अवसर्पिणी (avasarpiṇī) (L.)

(also with गणक (gaṇaka), कवि (kavi), दैवज्ञ (daivajña), पण्डित (paṇḍita), भट्ट (bhaṭṭa), मिश्र (miśra), यतीन्द्र (yatīndra), वाजपेयिन् (vājapeyin), शास्त्रिन् (śāstrin) etc.) the name of various authors and others (Inscr., Cat.)

= अग्नि (agni) (L.)

= वसुदेवता (vasudevatā) (L.)

= शुद्ध (śuddha) (L.)

name of the mother of the 11th अर्हत् (arhat) of the present अवसर्पिणी (avasarpiṇī) (L.)

Source: wiktionary.org