stiff, unyielding, inflexible, exact.
Yes, rigid is an adjective. Rigidly is an adverb. Rigidity is a noun.
The answer to the analogy "rigid is to flexible" is "strict is to lenient." Just as rigid and flexible are opposite in terms of stiffness, strict and lenient are opposite in terms of severity.
The word "pliable" completes the analogy. Rigid is to flexible as inflexible is to pliable.
Graphene is considered the most rigid material known to man.
Something rigid is stiff and not easily bendable or flexible. It does not easily change shape or position.
Neither rigid nor initially are synonyms for worse.
rigid, firm, inflexible, unbending
stiff, strict, rigid, inhuman
tight, stretched, rigid
Solid, strong, tough, dense, rigid, firm and compact
Meticulous, fastidious, finicky, scrupulous, picky, punctilious, exact, rigid...
stiff, tight, rigid, close, flexed, firm, tense, unyielding
There are many synonyms of the word prescriptive, which means to be authoritarian. These include the words accepted, sanctioned, authoritative, rigid, prescribed and authoritative.
Some synonyms for the verb stiffened are made rigid, firmed, fixed, hardened, petrified, reinforced, or tensed.
straight, upright, tough, disciplinary, harsh
Adjectives that are synonyms for prim can include demure, formal, proper, prudish, or stuffy. The last two have negative connotations (too stiff, rigid, or stern).
Rigid is immovable, unbending. Semi-rigid can move in a limited way.