1. Vigilant
   "must remain on your guard in such a situation"
   - on guard, on one's guard, upon one's guard

See also: wary

• hardwood
• hardworking
• hardy
• hare
• hare and hounds
• Hare Krishna
• hare wallaby
• hare's-foot bristle fern
• hare's-foot fern
• harebell
• harebrained
• Haredi
• hareem
• Harefoot
• harelip
• harelipped
• harem
• Hargeisa
• Hargreaves
• haricot
• haricot vert
• haricots verts
• Harijan
• harikari
• harissa