1. Fully awake
   "so excited she was wide-awake all night"
   - unsleeping 
2. Fully alert and watchful
   - heads-up

See also: alert, awake, watchful

• hickory pine
• hickory tree
• hidalgo
• Hidatsa
• hidden
• hidden agenda
• hidden reserve
• semi-wild
• semiabstract
• semiannual
• semiannually
• semiaquatic
• semiarid
• semiautobiographical
• semiautomatic
• semiautomatic firearm
• semiautomatic pistol
• semibreve
• semicentenary
• semicentennial
• semicircle
• semicircular
• semicircular arch
• semicircular canal
• semicolon