stiff, rigid; starched, very formal; strong-willed, stubborn; frozen solid, rigid due to cold; erect, hard, stiff (having an erect penis; translates in some contexts to erection, boner, stiffy)
“Me preocupa que sus codos estén tan tiesos, doctor.” — Doctor, I'm worried her elbows are so stiff.
Synonyms: rígido, inflexible, muerto, pelado
Inherited from Old Spanish teso, attested from the 1300s (in the Sumas de historia troyana, and later the Rimado de Palacio), inherited from Latin tēnsus. Compare the borrowed doublet tenso. Coromines & Pascual have Cristóbal de las Casas's Vocabulario de las lenguas española y toscana (1570) as their first known attestation with the diphthong -ie-, a development perhaps influenced by the conjugation él/ella tiende, of tender.