1. Conducted with or marked by hidden aims or methods
   "an undercover investigation"
   - clandestine, cloak-and-dagger, hole-and-corner, hugger-mugger, hush-hush, secret, surreptitious, underground

See also: covert

Encyclopedia: Undercover

• outshout
• outside
• outside caliper
• outside clinch
• outside door
• outside loop
• outside marriage
• outside mirror
• outsider
• outsider art
• outsize
• outsized
• outskirt
• outskirts
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• outsole
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• outspoken
• outspokenly
• outspokenness
• outspread
• outstanding
• outstandingly