Yup 'lightswitched' is an SV term. It comes from a line Lex said in season 1 or 2: 'the road to darkness is a journey not a lightswitch'. Fandom cried 'lightswitch' on Lex's journey MANY a time between then and his final descent and I usually passionately disagreed with them since I think that SV did a good job of showing the gradual darkening of Lex and the reasons why. But SV does suffer from doing the dance of one step forward two steps back a lot of the time--often there is less consistency between sequential episodes than there is if you look at a season as a whole. And that's partly to do with the comic book style they go for and their obsession with iconic moments. Anyway. I diverge...

My main complaint about the term lightswitch is that it's been overused by people who haven't been bothered to look deeper beneath the surface or at the bigger picture on the show. They felt a disconnect and immediately labelled it 'lightswitch' when it wasn't... and if I'm guilty of that with Lois I will suck it up and admit it. I hope I am! I hope someone can tell me where this sudden liking of Clark came from, plausibly, within canon.