Quick answer
en plan
Natural: like / sort of / as in
Literal: “in plan”
How it is used
Fuimos en plan tranquilo.We went in a relaxed way.
Me dijo, en plan, que no venía.He told me, like, that he wasn’t coming.
Íbamos en plan turista.We were going full tourist mode.
Es en plan broma.It’s meant as a joke.
Where it is said
It is very much a Spain thing, especially under forty; in Latin America the equivalent filler is usually <b>como</b> or <b>tipo</b>.
A mini dialogue
— ¿Cómo fue la cena?— How was the dinner?
— Bien, en plan informal.— Good, pretty casual.
Watch out
en plan
It has nothing to do with making plans, so tenemos un plan and en plan are two different things.
Check yourself
Which sentence uses “en plan” correctly?