1.
a small area of lower air density or a downward air current that makes an aircraft abruptly lose height
2.
an air bubble that impedes the flow of liquid or gas in a pipe
3.
an area where the air pressure is low that makes an aircraft fall suddenly to a lower level
4.
a small enclosed area that becomes filled with air
1.
a small area of lower air density or a downward air current that makes an aircraft abruptly lose height
2.
an air bubble that impedes the flow of liquid or gas in a pipe
3.
an area where the air pressure is low that makes an aircraft fall suddenly to a lower level
4.
a small enclosed area that becomes filled with air