Definitions of stem:

• noun:   the tube of a tobacco pipe
• noun:   a turn made in skiing; the back of one ski is forced outward and the other ski is brought parallel to it
• noun:   cylinder forming a long narrow part of something
• noun:   a slender or elongated structure that supports a plant or fungus or a plant part or plant organ
• noun:   front part of a vessel or aircraft
• noun:   (linguistics) the form of a word after all affixes are removed

  Example: "Thematic vowels are part of the stem"

• verb:   grow out of, have roots in, originate in

  Example: "The increase in the national debt stems from the last war"

• verb:   cause to point inward

  Example: "Stem your skis"

• verb:   stop the flow of a liquid
• verb:   remove the stem from

  Example: "For automatic natural language processing, the words must be stemmed"

• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #17968)