NATO refers to airborne air defence as counter-air and naval air defence as anti-aircraft warfare. Missile defence is an extension of air defence as are initiatives to adapt air defence to the task of intercepting any projectile in flight.
TBH usually means To Be Honest, but it can also mean Honest Opinion. To Be Honest was the original meaning of TBH, but nowadays it often just means Honest Opinion or Honest Comment. Of note, TBH was originally used with a blunt or slightly antagonistic statement to suggest the statement derived from sincerity.
What is meant by the TBN of oil? TBN stands for Total Base Number, which is a measure of how well the oil can neutralize acidic combustion byproducts. The higher the TBN of new oil is not always a good indicator of how well the TBN will last when the oil is subject to extreme heat and corrosive exhaust gases.