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1. A continuous parallel folding in an accordion-like fashion, that is with folds alternatively made to the front and back in zig-zag folds.
   "Seen from above, concertina folds resemble a Z or M or series of zigs and zags.";
   - accordion fold, zig-zag fold, z-fold

Derived forms: concertina folds

Type of: bend, crease, crimp, flexure, fold, plication