selfish, arbitrary
恣 centers on acting purely from one's own desires without external restraint: selfishness and arbitrary behavior. Both given meanings flow from this idea of unchecked personal will.
恣 combines 次 (next, order) with 心 (heart/mind), suggesting a mind that follows its own order or desires without restraint. The exact historical development is uncertain, but the phono-semantic structure with 次 contributing the sound シ is plausible.
The top part 次 looks like a person leaning over, and the bottom 心 is the heart. Imagine someone leaning only toward their own heart's wishes, ignoring others—that's selfish and arbitrary.
For シ, picture a selfish person saying 'She' wants everything her own way: 'She' -> シ, and her heart 心 follows only her own order 次.