Sealioning is a trolling or harassment tactic in online discussions and blogs. It involves the attacker asking relentless and insincere questions or requests for evidence under the guise of civility and a desire for genuine debate. These requests are often tangential or previously addressed, and the attacker maintains a pretense of civility and sincerity, while feigning ignorance of the subject matter. Sealioning is aimed at exhausting the patience and goodwill of the target, making them appear unreasonable.
Sealioning has been described as "incessant, bad-faith invitations to engage in debate". Sealioning can be performed by an individual or by a group acting in concert.
Internet trolls sometimes engage in what is called 'sealioning'. They demand that you keep arguing with them for as long they want you to, even long after you realize that further discussion is pointless. If you announce that you want to stop, they accuse you of being closed-minded or opposed to reason. The practice is obnoxious. Reason should not be silenced, but it needs to take a vacation sometimes. ( Walter Sinnott-Armstrong, Think Again: How to Reason and Argue (June 2018)
Rhetorically, sealioning fuses persistent questioning—often about basic information, information easily found elsewhere, or unrelated or tangential points—with a loudly-insisted-upon commitment to reasonable debate. It disguises itself as a sincere attempt to learn and communicate. Sealioning thus works both to exhaust a target's patience, attention, and communicative effort, and to portray the target as unreasonable. While the questions of the "sea lion" may seem innocent, they're intended maliciously and have harmful consequences. (Amy Johnson, Berkman Klein Center for Internet & Society)