antiparallel adjective 3noun 1forms 1 adjective3 •(of vectors) Parallel but in opposite directions. •Describing the orientations of the two strands of DNA. •Describing two beta strands comprising a protein's secondary structure that are aligned and hydrogen bonded but where the vectors describing the amino- and carboxy-terminal ends of each strand are oriented 180° relative to one another. noun1 •A line that forms equal angles with two other lines, but in opposite directions. formsantiparallels
