Of a law, a treaty, an institution, a condition of things: Firmly settled, established, unchangeable.

Well-founded or established, solid, firm. Of instruction: Thorough.

Not liable to fail or vary. Of government, institutions, customs, etc.: Securely established; not liable to destruction or essential change. Often…

Of non-material things: Fixed, settled, established. Of a decree, law, or sentence: Immutable.

Of a feeling, idea, reason, etc.: that has a firm basis or foundation; based on good grounds. Cf. well-founded, adj.

Rooted, enrooted.

Firmly established. Also: securely attached.

That does not move or change; having a fixed place or position; stationary; established. Obsolete.

Of a strong, firm, or substantial nature or quality; not slight or flimsy. Of things (or persons), in figurative applications.

Made firm, strengthened, settled, firmly established, etc.: see the verb.

In senses of the verb.

Firmly established; difficult to challenge or dislodge; (hence) unlikely to change.

That has a firm or solid basis; enduring; important, significant, weighty; of substantial extent or amount, considerable.

Made stable. Prevented from oscillating or moving.