1 [only before noun]
below something else, especially below something of the same type [≠ upper]:
Nina chewed her lower lip anxiously.
Ruth went down to the lower deck (=lower level on a ship).
your lower limbs (=your legs)
2 [only before noun]
at or near the bottom of something [≠ upper]:
the lower slopes of the mountain
She suffers with pain in her lower back.
smaller in number or amount [≠ higher]:
Temperatures will be lower over the weekend.
4 [only before noun]
less important than something else of the same type [≠ higher]:
the lower levels of management