The word "jump" holds a strong significance in the short story "Jump" by Nadine Gordimer.
Thematically speaking, the main character is a counterrevolutionary soldier in Apartheid South Africa who had originally joined the cause against the black government in his home country of Mozambique.
After witnessing what really goes on with the black prisoners taken by the counterrevolution (mainly child and physical abuse, sex trade and other atrocities), the main character "jumps" from his revolutionary faction and goes right to the office of the black revolutionaries to surrender himself and to pass on confidential information.
The man is in awe at his own actions; he would have never considered making that kind of jump, not only from his people, but from the ingrained ideals with which he was brought up. What was to happen next? Who was he going to become after "the jump". He does it, regardless. As a result, he now lives secluded in a Mozambique hotel, estranged from everybody and always in fear of his life. This political "jump" is the thematic significance of the word.
"Jumping" is also important to the story because the word will take on a completely different meaning toward the end; it will signify the solution to the man's problem: the possibility of jumping out of the top of the roof of his hotel and end the misery and isolation that is eating the main character alive.
Therefore, the word "jump" is an effective title to the story considering that the actions of the main character encompass the different meanings of one same word.