Is there any legit way in which whoever made this trade could have got a wind of a potential acquisition without relying on inside knowledge?
replies(3):
Example: You watch the front door of an office building. From seeing who walks in, you ascertain with 99% probability that companies X and Y are working on some kind of big deal. If you're just a random person with no relationship to those companies, you can trade on this information.
(Not legal advice! Don't do this unless you are sure it is OK! Which I am not!)