American & Australian, informal, American, very informal!

someone who is always trying to seem more clever than everyone else in a way that is annoying.

Okay, wise guy, if you're so damned smart, you can tell everyone how it's done!

He's just some wise-ass who thinks he knows all the answers.

• green-fingered
• green with envy
• greet someone with open arms
• greet something with open arms
• greet with open arms
• grey area
• grey matter
• Grim Reaper
• grin and bear it
• grind to a halt
• grind to a standstill
• grin from ear to ear
• grin like a Cheshire cat
• grist to the mill
• grit teeth
• grit your teeth
• gross out
• gross someone out
• ground-breaking
• groves of academe
• grow by leaps and bounds
• growing pains
• grow like Topsy
• grow on
• grow on you