Definitions of plunk:

• noun:   (baseball) hitting a baseball so that it drops suddenly
• noun:   a hollow twanging sound
• verb:   pull lightly but sharply with a plucking motion
• verb:   drop steeply
• verb:   make or move along with a sound as of a horse's hooves striking the ground
• verb:   set (something or oneself) down with or as if with a noise
• adverb:   with a short hollow thud
• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #11650)