at will Definition

will²
noun

1. The power of conscious decision and deliberate choice of action.

Example: free will
Example: exercise one's will
2. One's own preferences, or one's determination in effecting them.

Example: a clash of wills
Example: against my will
3. Desire or determination.

Example: the will to live
Thesaurus: desire, inclination, volition, want, wish, pleasure, yearning, craving, longing, hankering; Antonym: indifference.
4. A wish or desire.
5a. Instructions for the disposal of a person's property, etc after death;
5b. The document containing these.
6. One's feeling towards someone else.

Example: felt no ill-will towards her

verb willed, willing

1. To try to compel someone by, or as if by, exerting one's will.

Example: willed herself to keep going
2. formal
To desire or require that something be done, etc.
Example: Her Majesty wills it
Thesaurus: command, insist, decree, order, demand, enjoin, request; wish, want, prefer.
3. To bequeath something in one's will.

Idiom: at will

As and when one wishes.

Idiom: with a will

Eagerly; enthusiastically.

Idiom: with the best will in the world

Note: with negatives
No matter how willing one is or how hard one tries.

Etymology: Anglo-Saxon willa.