Rigid means stiff and unbending. A rigid frame, rigid plastic, a rigid structure.
Of materials it is a neutral engineering property: rigidity is what stops a structure deforming under load. Of rules and people it is a criticism meaning inflexible: rigid rules, a rigid approach. Rigid with fear means frozen. Note rigidity; rigor mortis, which is the stiffening after death and comes from the same Latin; and that rigid and rigorous share a root but not a tone — rigorous is a compliment.
1adjectiverigidStiff and unbending, of a material.
“The tent has a rigid frame, so it stays up in strong winds.”
synonyms: inflexible, stiff
2adjectiveunwillingUnwilling to change, of rules or people.
“The school has rigid rules about uniform, and even the wrong socks get you in trouble.”
rigid is a quality of stiffness.
Also accepted in games: inflexible
Latin rigidus comes from rigere, to be stiff — the same root as rigour and rigor mortis. The word has meant physical stiffness since Latin and acquired the criticism in English.
Proto-Indo-European
*Hreyǵ-
Latin
rigidus
Middle English
rigide
English, today
rigid
Built from
From Middle English rigide, from Latin rigidus. From Middle English rigide, from Latin rigidus (“stiff”), from rigeō (“to be stiff”). Compare rigor. Merged with Middle English rigged, rygged, rugged (“upright like a spine, rigid”) literally “ridged”.
Etymology from Wiktionary, CC BY-SA
Practised in Sharper Adjectives, Texture & Touch