(adjective)
having a continuous, regular, and even surface or consistency, lacking lumps, indentations, or projections;
e.g. The bottom of the stream was covered with smooth stones.
(adjective)
having an even flow or course and not having any jerks, used to describe the manner of motion;
e.g. The horse moved with a smooth trot, so that the rider didn't get bumped around.
(adjective)
not having any difficulties, impediments, or problems, used to describe the course of an event, activity, or process;
e.g. Proper organization and adequate arrangements will ensure the smooth functioning of the event.
(adjective)
considerably charming, suave, and courteous, often excessively so, to the point of seeming insincere;
e.g. He had a smooth manner that made him seem dishonest.
(verb)
to make something have a regular and flat appearance or surface, to rid something of irregularities;
e.g. He used a hand to smooth the creases in his shirt.
(verb)
to successfully address difficulties, obstructions, or problems in something, or to remove such impediments from something;
e.g. She was summoned to smooth out the conflicts between them.