Definitions of plop:

• noun:   the noise of a rounded object dropping into a liquid without a splash
• verb:   drop with the sound of something falling into water
• verb:   drop something with a plopping sound
• verb:   set (something or oneself) down with or as if with a noise
• adverb:   with a short hollow thud

  Example: "Plop came the ball down to the corner of the green"