Question that demands an explanation

• "Could you explain?"
• "Why?"
• "Care to elaborate?"
• In what way?
• "Care to explain?"
• "In what way?"
• "In what sense?"
• Request for elaboration

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Howso \How"so\, adv. Howsoever. [Obs.]

Wiktionary Word definitions in Wiktionary
adv. 1 however#Conjunction, in whatever manner. 2 However, to whatever extent.