Timothy should turn away from meaningless discussions that characterize the world, on the other hand (cf. 1 Timothy 1:3-4; 1 Timothy 4:7; 1 Timothy 6:20). These only provide an atmosphere in which ungodliness grows. [source][source][source]
"It may be that these people regarded themselves as "progressives" and that Paul picks up the verb from their usage, ironically indicating that their progress is in ungodliness." [1][source]
Those who engage in such discussions spread poison that eventually corrupts the body of Christ. Gangrene is decay of tissue in a part of the body when the blood supply is obstructed by injury, disease, or some other cause. Medical writers of Paul"s day used this term (Gr. gangraina, only here in the New Testament) to describe a sore that eats into the flesh. [2][source]