Dictionary Definition:
じんしんじこ (n) traffic accident resulting in personal injury or death

Gavin Definition:
Some git decided he would end his life. Chosen method was to jump in front of a train on the JR Joban line during rush hour. Causes a whole load of incovenience for other people in the process.

Now, we all know Japan suffers a lot from suicides, but recently its been getting really bad.
BBC Link.