preterlasi

Take it apart and the meaning falls out. Preter is the preposition of motion past something: li iris preter la domo, he walked past the house. Lasi is to let or to leave. Put them together and you have the picture exactly: the thing goes past, and you let it. Compounding two roots like this, preposition first, is one of the commonest patterns in the language - see Compounding.

Both English senses follow from the same image without any extra learning. You preterlasi an opportunity, because it went past and you did not take it. You preterlasi a word when reading aloud, or a paragraph when editing, because it went past and you did not catch it. There is no separate word to learn for omit.

The family is worth having as a set, because each member moves a different thing:

• preterlasi - the thing moves past you and you let it.
• preterpasi - you move past the thing.
• preteriri - you walk past it.
• pretervidi - your eye goes over it without registering, to overlook.

For a train you failed to board, maltrafi is the more usual verb - that is a miss of aim rather than a miss of attention. And note the accusative: preterlasi is transitive, so what you missed takes -n.