https://lemmygrad.ml/comment/2927106

It's essentially the opposite of an ultra. An ultra oversteps the political consciousness of the masses where a tailist caters to the reactionary elements of the working class. A communist vanguard party needs to lead, elevate, and unite the masses with integrity while keeping in mind of the masses current political consciousness in order to gain their overwhelming support.

https://en.prolewiki.org/wiki/Library:On_Coalition_Government

Commandism is wrong in any type of work, because in overstepping the level of political consciousness of the masses and violating the principle of voluntary mass action it reflects the disease of impetuosity. Our comrades must not assume that everything they themselves understand is understood by the masses. Whether the masses understand it and are ready to take action can be discovered only by going into their midst and making investigations. If we do so, we can avoid commandism. Tailism in any type of work is also wrong, because in falling below the level of political consciousness of the masses and violating the principle of leading the masses forward it reflects the disease of dilatoriness. Our comrades must not assume that the masses have no understanding of what they themselves do not yet understand. It often happens that the masses outstrip us and are eager to advance a step when our comrades are still tailing behind certain backward elements, for instead of acting as leaders of the masses such comrades reflect the views of these backward elements and, moreover, mistake them for those of the broad masses.

---Mao Zedong. "On Coalition Government" (April 24, 1945), Selected Works, Vol. III, p. 316.*

Definition

https://en.prolewiki.org/wiki/Tailism