This is a short, back, open sound.
“Back” means that the tongue is positioned as far back as possible in the mouth without creating a constriction that would be classified as a consonant.
“Open” means that the tongue is positioned as far as possible from the roof of the mouth. Open vowels are sometimes also called low vowels in reference to the low position of the tongue.
Watch the video and practise this vowel here (no comments about the woman’s hairstyle, please!).