tamper

from The Century Dictionary.

• noun One who tamps, or prepares for blasting by stopping the hole in which the charge is placed.
• noun An instrument used in tamping; a tamping-bar or tamping-iron.
• To experiment rashly; busy one's self unwisely or officiously; meddle: usually followed by with in this and the other senses.
• To interfere, as for the purpose of alteration; make objectionable or unauthorized changes (in): as, to tamper with a will or other document.
• To use secret or underhand measures; exert unfair or corrupt influence; especially, to use improper persuasions, solicitations, bribery, etc.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who tamps; specifically, one who prepares for blasting, by filling the hole in which the charge is placed.
• noun An instrument used in tamping; a tamping iron.
• intransitive verb To meddle; to be busy; to try little experiments.
• intransitive verb To meddle so as to alter, injure, or vitiate a thing.
• intransitive verb To deal unfairly; to practice secretly; to use bribery.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A person or thing that tamps.
• noun A tool used to tamp down tobacco in a pipe.
• verb intransitive To alter by making unauthorized changes; to meddle.
• verb in professional sports To discuss future contracts against league rules with a player.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb intrude in other people's affairs or business; interfere unwantedly
• noun a tool for tamping (e.g., for tamping tobacco into a pipe bowl or a charge into a drill hole etc.)
• verb play around with or alter or falsify, usually secretively or dishonestly