Quenching the Spirit means despising or neglecting his gifts, refusing to express spiritual emotion, and resisting his fruit – so we must be careful not to quench the Holy Spirit, by indulging carnal lusts and affections, minding only earthly things. Source Website

Thess. 5:19 (KJV) But you can also quench the Holy Spirit
Ephesians 4:30 (KJV) And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.
Hebrews 10:29 (KJV) Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?

quenched meaning:
1. to put out or extinguish.
2. to subdue, to suppress, stifle
3. unresponsive to the working and guidance of

How do we quench the Holy Spirit?
via contempt of; disdain of, rejection of, stop listening to, restraining the Holy Spirit, or not complying with, but becoming worldly minded.