Req (H7386) means empty, vain, or without substance. It describes the hollow, purposeless existence of those who turn from God — as well as literal emptiness like an unfilled vessel. The related adverb reqam means 'empty-handed.'
Proverbs warns against following the worthless and vain. The Psalms contrast the 'empty' counsel of the ungodly (Psalm 2:1, 'why do the nations rage/conspire vainly') with the life-giving purposes of God. Paul warns against being taken captive by 'empty (kenos) philosophy' (Colossians 2:8). God sends none of His own away empty — He fills the hungry with good things (Luke 1:53).