Watch the Keep It Out online guitar lesson by TrueFire from Play Acoustic Guitar 6: Lick Vocabulary

Keep It Out - Trick 10 is a video guitar lesson presented by Matthieu Brandt and is sourced from 50 Chord Tricks You MUST Know.

Leaving out the third (major or minor) of a chord will get you a 'floating' sound, uneasy and uncertain. This chord trick works well, if you are looking for spooky progressions and mystifying atmospheres.