Definition from Wiktionary, the free dictionary
cantrip (plural cantrips)
- A spell or incantation; a trifling magic trick.
- 1791, Robert Burns, "Tam o' Shanter", lines 125-8, 
- 1951, C. S. Lewis, Prince Caspian, Collins, 1998, Chapter 12,
- I have some poor little skill—not like yours, Master Doctor, of course—in small spells and cantrips that I’d be glad to use against our enemies if it was agreeable to all concerned.
- 1976, Kyril Bonfiglioli, Something Nasty in the Woodshed (Penguin 2001, p. 422)
- For one thing, I've no intention of distributing cantrips and costly crucifixes to every rapable woman in the Parish of St Magloire.
- 1984, Anthony Burgess, The Kingdom Of The Wicked
- And when I say now the power of the name Jesus makes you whole, I indulge in no petty mountebank’s cantrips.
- 2009, James Patterson and Gabrielle Charbonnet, Witch and Wizard (Little, Brown and Company 2009, p. 148)
- But it sounds to me like you're in a totally different category. Not garden-variety cantrip stuff.
- A wilful piece of trickery or mischief
- ^ Chambers Dictionary, 1998, s.v.