Interferer

in·ter·fere  (ntr-fîr)

intr.v. in·ter·fered, in·ter·fer·ing, in·ter·feres

1. To be or create a hindrance or obstacle: loud talking that interfered with the other patrons' conversations; assistance that only interfered.

2. Sports To perform an act of interference.

3. To intervene or intrude in the affairs of others; meddle.

4. To strike one hoof against the opposite hoof or leg while moving. Used of a horse.

5. Physics & Electronics To cause interference.

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[Middle English enterferen, from Old French s'entreferer, to strike one another : entre-, between (from Latin inter-; see inter-) + ferir, to strike (from Latin ferre).]

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inter·ferer n.

inter·fering·ly adv.

Synonyms: interfere, meddle, tamper¹
These verbs mean to intervene unasked in the affairs of others and often in an impudent or indiscreet manner. Interfere implies action that seriously hampers, hinders, or frustrates: "Romantics of all ages can recall occasions when lust interfered with reason" Christine Gorman.
Meddle stresses unwanted, unwarranted, or unnecessary intrusion: "wholly unacquainted with the world in which they are so fond of meddling" Edmund Burke.
To tamper is to interfere by making unsought, unwelcome, often destructive changes or by trying to influence another in an improper way: "a large number of persons accused of . . . tampering with ballot boxes" James Bryce.