enuigi

Enuigi is a textbook case of the -ig- suffix, and once you see the mechanism you get several hundred verbs free.

Start from the root. Enui is what the bored person does: mi enuas means I am bored, and it takes no object. Add -ig- and you get the causative - the verb for making somebody else feel it. Enuigi therefore takes an object, and the object is the person who ends up bored: la libro enuigas min, the book bores me. The pair runs the same way everywhere in the language: morti / mortigi, sidi / sidigi, varma / varmigi.

Its mirror is enuiĝi, with -iĝ- instead. That suffix means becoming rather than causing, so mi enuiĝas is "I get bored", the change of state, where mi enuas is the state itself. Line the three up and the system is obvious: enui (be bored), enuiĝi (become bored), enuigi (make bored). The full account of the two suffixes and how to stop confusing them is at igi and iĝi.

Two derived forms are worth having straight away, because they are commoner than the verb. Enuiga is the adjective for the thing that does the boring - a boring lecture is enuiga prelego - and enuo is boredom itself. English uses "bored" and "boring" for these and learners routinely swap them; Esperanto's endings will not let you.