“Nor should there be obscenity, foolish talk, or coarse joking, which are out of place, but rather giving thanks” (Eph. 5:4).

Foolish talk is silly talk, empty talks that proceed from fools with no intellect. Coarse joking is anything that relates to sin (it could be sexual related, violent, gossiping etc).
Jokes that destroy man, jokes that involve ungodliness, any joke that will lead the receiver to sin is wrong in the sight of God.
“Let no corrupt word proceed out of your mouth, but what is good for necessary edification, that it may impart grace to the hearers” (Eph. 4:29).

“Avoid godless chatter, because those who indulge in it will become more and more ungodly” (II Timothy 2:16).
Godless chatter will produce an ungodly life with time. The Greek word for “chatter” is kenophonia, and is used to describe, “empty, foolish talk, talk which lacks significant content i.e. fruitless discussion.” (Pastor Jason Stewart).

“But avoid foolish disputes, genealogies, contentions, and strivings about the law; for they are unprofitable and useless” (Titus 3:9).
Arguing about the law is pointless and will lead to godless chatter, sometimes corrupt or unwholesome talks since you might try to buttress your point to convince your listener.