Re-articulation of your statements. Have you ever been in a meeting and your boss asked for input from everyone? People chime in and you say your piece only to have someone repeat your exact words minutes later. The first few times this happened to me, I immediately checked the person. And was miffed. But that made people only remember the outcome. 
Let me tell you how to do it and look like a winner. After your words are being owned and your boss ask the offender a clarifying question, politely interject "that's a good question" and proceed to answer. The reason you don't wait for your colleague to defer back to you for a response is because it then looks as if he or she were the originator. And even though you spoke first, the statement was heard from their mouth last. 
Watch to see who this person steals words from. It could be how they process or they could be a straight saboteur. And you could have a private conversation with them.