I would put the file in Excel and parse out the first word (or two words) into a separate column so that the term is in one column and the definition is in another. Then you can save the file as a csv file and import it into Access.
You would have to use a function to read the first space after the first word. It wont work on two word terms, but you can go back and edit those manually.
Let's assume your target cell is A1
=LEFT(A1, FIND(" ", A1, 1))
This will extract the first word (before the first space) from the text.
=RIGHT(A1, LEN(A1) - FIND(" ", A1, 1))
This will get the rest of the text. Place this in the next cell over. Then you need to copy the two columns you just created, click on Sheet 2 and Click Edit --> Paste Special --> Paste Values. Save the current sheet as a csv file and then you can import it into access.