What does the "re-review" mean? We have written a revised manuscript since the original version is received a decision of "major revision."
Since the status remained "reviewer assigned," we sent a mail with requesting clarification. 
The journal editor office replied that the section editor decided to seek re-review for our manuscript given the nature and extent of the revisions requested. 

Does "re-review" mean the revision is pending for the original reviewers' comments, or that the section editor sought other reviewers to re-examine the revision for different opinions, or something else?
It could be either, but it usually goes back to the reviewers that requested the major modifications. Whoever the editor sent it to, it means that it is being reviewed again in full.