At the start of the year, this year our Year 7's were each given a dictionary. Now a typical introduction for me is to assign groups a different keyword to look up- read out and listen to as a class. Then I ask 2-3 students to think about how to re-phrase the definition in their own words.
We discuss sentence order, clarity, quality of explanation, ease of understanding etc. When we're all happy the definitions are recorded in sketchbooks.
To quote the '5 minute lesson plan', this enhances the 'stickability' of keywords more than just defining them straight out on my Powerpoint.
As an example, this is what they came up with for 'cliffhanger'-
an ending that is sudden and unclear in a story or film. It is aggravating, intense and exciting because it is uncertain. It makes you want to find out about the next part of the story.