depression definition. A period of drastic decline in the national economy, characterized by decreasing business activity, falling prices, and unemployment. The best known of such periods is the Great Depression, which occurred in the 1930s.
A variometer â also known as a rate of climb and descent indicator (RCDI), rate-of-climb indicator, vertical speed indicator (VSI), or vertical velocity indicator (VVI) â is one of the flight instruments in an aircraft used to inform the pilot of the rate of descent or climb.
Vertical means up and down; so the vertical velocity is an indication of how quickly an object is rising or falling. If the object is moving at an angle (such as an airplane taking off or landing) then it would be more accurate to call it the vertical component of the object's velocity. Aries Dell.