tamper

A person or thing that tamps.

A tool used to tamp something down, such as tobacco in a pipe.

A railway vehicle used to tamp down ballast.

An envelope of neutron-reflecting material in a nuclear weapon, used to delay the expansion of the reacting material and thus produce a longer-lasting and more energetic explosion.

To make unauthorized or improper alterations, sometimes causing deliberate damage; to meddle (with something).

“The alarm had been tampered with and didn’t go off when it should have.”

To try to influence someone, usually in an illegal or devious way; to try to deal (with someone).

“Prosecutors argued that he would tamper with witnesses if bail was granted.”

To meddle (with something) in order to corrupt or pervert it.

To involve oneself (in a plot, scheme, etc.).

To attempt to practise or administer something (especially medicine) without sufficient knowledge or qualifications.

(in professional sports) To discuss future contracts with a player, against league rules.