adj

• (of an action) Natural; unconstrained.
  "In order for a reading to be smooth and effortless, readers must be able to recognize and read words accurately, automatically, and quickly."
• (of a motion) Unbroken.
  "Demonstrate first by the numbers and then as one smooth movement."
• (chiefly of water) Placid, calm.
  "As we worked to the southward, we picked up fair weather, and enjoyed smooth seas and pleasant skies."
• (of an edge) Lacking projections or indentations; not serrated.
  "A leaf having a smooth margin, without teeth or indentations of any kind, is called entire."

noun

• (statistics) The analysis obtained through a smoothing procedure.
  "A smooth of the potato data set has already been given in Figure 1.2."

verb

• (transitive) To make smooth or even.
  "She smooths her skirt, looking as composed and ladylike as possible."
• (transitive) To reduce to a particular shape or form by pressure; to press, to flatten.
  "to smooth cloth with a smoothing iron"
• (transitive) To make straightforward or easy.
  "Caracas can be a tough place but the tremendously good-natured caraqueños smoothed my passage every step of the way."
• (transitive) To calm or palliate.
  "to smooth a person's temper"