- automatic winch
- automation line
- autonomous state
- autopsy
- auxiliary bridge
- auxiliary entrance
- auxiliary production
- auxiliary reinforcement
- auxiliary taxiway
- avalanche baffle
- avant-corps
- average alluminance
- average head
- average infiltration
- average misclosure
- average salary
- average specimen
- awake
- awning sash
- axial
- axial composition
- axial elongation
- axial impact
- axially symmetric
- axis
- axisymmetrical stress
- axle driving
- axle trailer
- babbit lined
- baby
- bachelor flat
- back
- back coat
- back coupling
- back door
- back elevation
- back filler
- back fillet
- back gutter
- back hearth
- back hoe
- back hole
- back lining
- back lintel
- back margin
- back matter
- back nailing
- back pass
- back putty
- back reading
- back river
- back room
- back saw
- back sawn
- back sight
- back siphonage
- back slab
- back slooper
- back stage
- back stair
- back stop
- back street
- back surge
- back terminal
- back timbering
- back trough
- back up
- back veneer
- back yard
- back-forms
- back-set
- back-shore
- backband
- backbone
- backcut
- backdigger
- backfill
- backfill compactor
- backfiller
- backfillet
- backfilling
- backfilling soil
- backfire
- backflow
- backflow connection
- background
- background color
- background heater
- background heating
- background level
- background noise
- background process
- background sound
- backing
- backing bevel
- backing board
- backing paper
- backing piece
- backing ring
- backing sand