Verbal Irony is a type of irony. Remember, irony is the incongruity between what is expected to happen and actually happens. Verbal irony is one of the three types of irony (Verbal, situational, and dramatic). Think of verbal irony as when ironic statements are intentionally said or distributed through verbal communication as a means of saying the opposite of what is truly meant.
In his novel Breakfast of Champions, he says “as pleasant and relaxed as a coiled rattlesnake.” Clearly a coiled rattlesnake would not be pleasant, and so we have verbal irony.