Real Dictionary

lower
You can use lower to refer to the bottom one of a pair of things.

lower in American English 1
in a place or on a level below another
adjective
intransitive verb: to become lower, grow less, or diminish, as in amount, intensity, or degree
noun: a denture for the lower jaw
transitive verb: to cause to descend; let or put down

lower in American English 2
a frowning or threatening look
to scowl or frown
intransitive verb: to be dark and threatening, as the sky or the weather
noun: a dark, threatening appearance, as of the sky or weather

lower in British English 1
adjective: being below one or more other things
verb: to cause to become low or on a lower level; bring, put, or cause to move down

lower in British English 2
(esp of the sky, weather, etc) to be overcast, dark, and menacing
noun: a menacing scowl or appearance