It's a shame that your teacher is expecting you to define phrases out of context. As an intransitive verb, as in 'Time passed by', you could paraphrase as 'go on'. As a transitive verb, it has two forms, inseparable and separable: If you 'pass by something' you 'go past it' or even 'go to it' (as in 'Pass by the store on your way home') If you 'pass something/someone by', it means that you omit, neglect, or fail to notice it, as in 'That piece of news passed me by'. These are just a few examples of the many uses and meanings of 'pass by'. Your teacher is asking you to do the impossible.

"pass by" does not need the word "by." So, you are looking for synonyms for the word "pass." Here are some: http://www.collinsdictionary.com/dictionary/english-thesaurus/pass I hope that helps.

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I would like to add that unlike Eddie, I do think that the word pass needs the preposition by. Sure, to pass works perfectly fine without "by" but "to pass" means something completely different and not necessarily includes the meaning of "to pass by". I agree on Su.Ki.`s explanation very much, and yes to pass by without a closer context can have many explanations and examples. Still! the preposition gives some limits for a definition! So, no to observe only "to pass" isn`t quite enough nor precise enough!

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