Fougasse
From Halopedia, the Halo wiki
Summary
A "fougass" is a barrel that is buried in the ground. It has Grenades in the bottom of it and can be filled with Napalm ("Fire" Fougasses) or spent shell casings ("Shrapnel" Fougasses). They can be remote detonated, sending fire and shrapnel upwards, above the ground. Normally they are used to destroy ground targets, but the Master Chief and his team of Spartans used ten fougasses to destroy five Covenant Banshee fliers during an engagement on Jericho VII.