Source : WordNet®

plump down
     v 1: drop heavily [syn: {plonk down}, {plank down}]
     2: set (something or oneself) down with or as if with a noise;
        "He planked the money on the table"; "He planked himself
        into the sofa" [syn: {plank}, {flump}, {plonk}, {plop}, {plunk},
         {plunk down}, {plump}]