What does the Bible mean by the term "world?" The world is that mass of humanity which has alienated itself from God and is therefore hostile to the cause of Christ. The world lives for frivolous and meaningless things.

The "world" to which the Bible refers to is BOTH the sinful world and the materialistic world. Something doesn't have to necessarily be sinful to be worldly.  For example: There is nothing wrong with owning a car or a motorcycle, but you can easily turn that object into a god that consumes your heart and mind, and that is sinful. God warns us about ALL THAT IS IN THE WORLD: the Lust of the eyes, and the LUST of the flesh, and the PRIDE of life. So many people today are filled with wicked pride, they don't care about Truth, or about the Lord Jesus Christ.