It could be a
Beaked Yucca (Yucca rostrata 'Sapphire Skies'), but the leaves are just too fat for yucca. Usually yuccas have very thin, pointy leaves, almost stringy at times.
But I just don't see what else it could be (and it's not an agave?) so it probably is a yucca. And it looks like there's maybe a flower stalk(s) growing from the middle? That's how yuccas flower.
