Reverie
Etymology
From French “rêverie,” from Old French “resverie” (wildness, delirium), from “resver,” to wander or rave (modern French “rêver,” to dream), whose ultimate origin is uncertain. The earlier English senses carried notions of raving and wild fancy; over time the word softened into the gentle, agreeable mind-wandering it names today.
noun · /REV-uh-ree/
A state of pleasant, absorbed daydreaming in which the mind drifts free of the present.
What it names
The soft, untethered drift of thought when you stop attending to the world and wander somewhere warmer inside your head.
Example
The lecture washed over him as he slipped into a reverie about the summer he spent on the coast.
Related idea
A daydream is often a single imagined scene; reverie names the enveloping, dreamy condition of being lost in thought, contents and all.