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

• bride-to-be
• bridecake
• bridegroom
• bridesmaid
• bridewell
• bridge
• bridge agent
• bridge circuit
• bridge deck
• bridge hand
• bridge over
• bridge partner
• bridge player
• bridge whist
• bridgeable
• bridged-T
• buckbean
• buckbean family
• buckboard
• bucked up
• buckeroo
• bucket
• bucket along
• bucket seat
• bucket shop