having existence or being or actuality; "an attempt to refine the existent machinery to make it more efficient"; "much of the beluga caviar existing in the world is found in the Soviet Union and Iran"
line thrown from a vessel that people can cling to in order to save themselves from drowning
line that raises or lowers a deep-sea diver
support that enables people to survive or to continue doing something (often by providing an essential connection); "the airlift provided a lifeline for Berlin"; "she offered me a lifeline in my time of grief"
the arithmetic operation of summing; calculating the sum of two or more numbers; "the summation of four and three gives seven"; "four plus three equals seven"
a concluding summary (as in presenting a case before a law court)
(physiology) the process whereby multiple stimuli can produce a response (in a muscle or nerve or other part) that one stimulus alone does not produce