Ooh, DBSK. I haven't heard that song, but I think the word is probably 싶어 [ship'ô]. It's the present tense for the verb "to want".
싶다 - to want
싶어(요) - I want, you want, he/she/it wants, we want, you (pl.) want, they want
싶었어(요) - I wanted, you wanted, he/she/it wanted, we wanted, you (pl.) wanted, they wanted
싶겠어(요) - I will want, you will want, he/she/it will want, we will want, you (pl.) will want, they will want