Something that blocks out light prevents it from reaching a place. Thick chipboard across the window frames blocked out the daylight Those clouds would have cast shadows that would have blocked some sunlight out
plan where and when songs should be inserted into a theatrical production, or plan a theatrical production in general indicate roughly; "We sketched out our plan
If someone blocks out a thought, they try not to think about it. She accuses me of having blocked out the past I had to block the thought out of my mind
{i} resist, protective coating which covers part or all of an object and inhibits an effect or reaction (such as paint which prevents water from penetrating)