1. Holding tenaciously or stubbornly to a purpose, opinion, or course of action: a pertinacious heretic; pertinacious defiance.
2. Extremely persistent or unyielding: pertinacious researchers.
[From Latin pertināx, pertināc- : per-, per- + tenāx, tenacious (from tenēre, to hold; see ten- in the Appendix of Indo-European roots).]
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