echelon

Từ điển WordNet v3.1 - WordNet Dictionary

noun

1. a body of troops arranged in a line
• Topics:
military, armed forces, armed services, military machine, war machine
• Hypernyms:
military unit, military force, military group, force
2. a diffraction grating consisting of a pile of plates of equal thickness arranged stepwise with a constant offset
• Hypernyms:
diffraction grating, grating