verb

• (ambitransitive) To make a short, audible inhalation, through the nose, as when smelling something.
  "The dog sniffed around the park, searching for a nice scent."
• (transitive) To say (something) while sniffing, such as in case of illness or unhappiness, or in contempt.
  ""He's never coming back, is he?" she sniffed while looking at a picture of him."
• (transitive) To perceive vaguely.
  "I don't know, of course, what your precious Radicals are planning to do, and I don't want to know; but I can sniff trouble in the air, nevertheless."
• (intransitive) To pry; to investigate in an interfering manner.
  "COOMBE: He got the clinch only last week — eighteen months. You see it's no good having anybody here as ain't got a^([sic]) unblemished character. We don't want to have the bluebottles come sniffing round here, do we?"

noun

• (countable) An instance of sniffing.
  "She gave the flowers a quick sniff to check they were real."
• (countable) A quantity of something that is inhaled through the nose.
• (countable, colloquial) A brief perception, or tiny amount.
  "Tottenham did have a sniff of goal when Defoe's drilled cross just eluded his strike partner at the far post but their best effort came early in the second half when Ryan Fredericks cut in from the right before firing into the side netting."
• (uncountable, slang) Cocaine.
  "He sold us some sniff and blow."