1. At the same time that
   "they were walking home whilst they were discussing the problem"
   - as, when, while 
2. Even though, in spite of the fact that
   "whilst I love you, I cannot marry you"
   - altho [US], although, though, tho', while

Encyclopedia: Whilst

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• redtail
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• reduce
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• reduced instruction set computer
• reduced instruction set computing
• reducer
• reducible
• reducing
• reducing agent
• reducing diet
• reductant
• reductase
• reductio
• reductio ad absurdum
• reduction
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• reductionism
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• reductive
• reductivism
• redundance
• redundancy