under cover
under cover of darkness
under fire
under house arrest
under lock and key
under oath
under one's arm
under one's breath
under penalty of
under pressure
under protest
under repair
under surveillance
under suspicion
under the guidance of
under the guise of
under the name of
under the protection of
under the table
under the weather
under the wire
underage
underbid
underbrush
undercarriage