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.
It's the abbreviation for Mean Corpuscular Hemoglobin. This is a measure for how much hemoglobin per red blood cell count. MCH stands for Mean Corpuscular Hemoglobin. It is a measure of the average amount of hemoglobin in each red blood cell.