decussate

Concise Oxford English Dictionary © 2008 Oxford University Press:
decussate technical

▶verb /dɪˈkʌseɪt, ˈdɛkəseɪt/ (of two or more things) cross or intersect. ▶adjective /dɪˈkʌsət/ 

• 1 shaped like an X.

• 2 Botany (of leaves) arranged in opposite pairs.

– derivatives
decussation noun.

– origin C17: from L. decussatus, past part. of decussare ‘divide crosswise’, from decussis (describing the figure X, i.e. the Roman numeral for 10), from decem ‘ten’.