Definition of "Under" :
adjective: lower in rank, power, or authority
"An under secretary."
adjective: located below or beneath something else
"The under parts of a machine."
adverb: further down
"See under for further discussion."
adverb: down below
"Get under quickly!."
adverb: below the horizon
"The sun went under."
adverb: below some quantity or limit
"Fifty dollars or under."
adverb: in or into a state of subordination or subjugation
"We must keep our disappointment under."
adverb: down to defeat, death, or ruin
"Their competitors went under."
adverb: into unconsciousness
"This will put the patient under."
adverb: through a range downward
"Children six and under will be admitted free."