Concealed, hidden.
Placed in a grave at a burial.
Actively engaged in fighting or dealing with the enemy; in battle or on maneuvers.
Away from the office, classroom, or laboratory; working with people or things in their natural environment.
Used other than figuratively or idiomatically: see in, field.
In a real-world setting, as opposed to the controlled conditions of a laboratory or the hypothesized parameters of a theoretical approach.