1.
If one thing blots out another thing, it is in front of the other thing and prevents it from being seen.
About the time the three climbers were halfway down, clouds blotted out the sun.
...with mist blotting everything out except the endless black of the spruce on either side.
PHRASAL VERB : V P n (not pron) , V n P
2.
If you try to blot out a memory, you try to forget it. If one thought or memory blots out other thoughts or memories, it becomes the only one that you can think about.
Are you saying that she’s trying to blot out all memory of the incident?...
The boy has gaps in his mind about it. He is blotting certain things out...
She has suffered an extremely unhappy childhood, but simply blotted it out of her memory.
= block out
PHRASAL VERB : V P n (not pron) , V n P , V n P of n