This much is correct.
Clarification on my previous post (which I'll admit was a little confusing). Lizards are ectotherms as opposed to endotherms.
And so is this.
Dinosaurs are also ectotherms as well. They are just great big lizards, in other words.
This, on the other hand... Dinosaurs may or may not have been ectotherms. There's a lot of debate and contradictory evidence about that. One of the latest views is that they actually had some features of both ectothermic and endothermic metabolisms (i.e., it may not be either-or, they may have been sort of in-between).
But even if they were ectothermic, that does *not* make them "big lizards". Ectothermia is hardly the defining characteristic of what makes a reptile a lizard. If it were, turtles and snakes would be "lizards" as well, and they're not.
Dinosaurs are their own distinct category, as specialized and different from lizards as lizards are from snakes/turtles.