All 5 Uses

allude
in
Heart of Darkness
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Then, alluding with a toss of the head to the tumult in the station-yard, 'When one has got to make correct entries, one comes to hate those savages—hate them to the death.'†
Chpt 1

alluding = making an indirect reference
He alluded constantly to Europe, to the people I was supposed to know there—putting leading questions as to my acquaintances in the sepulchral city, and so on.†
Chpt 1

alluded = indirectly referenced
The half-caste, who, as far as I could see, had conducted a difficult trip with great prudence and pluck, was invariably alluded to as 'that scoundrel.'†
Chpt 2
What we afterwards alluded to as an attack was really an attempt at repulse.
Chpt 2 *
He had, as he informed me proudly, managed to nurse Kurtz through two illnesses (he alluded to it as you would to some risky feat), but as a rule Kurtz wandered alone, far in the depths of the forest.†
Chpt 3

Definitions:

(1) (allude)
to make an indirect reference

The expression, no allusion can mean "not even an indirect reference"; i.e., neither a direct nor an indirect reference to something.
(2) (meaning too rare to warrant focus)