What is the meaning of ' Atom can be divided" and really is it possible that we can divide an atom.

Yes we have learned that the atom has component parts and that they can be separated by applying energy to the atom. As the amount of energy increases, the electrons (parts of the atom that orbit the nucleus) begin to fly off. If you apply enough energy, the nucleus of the atom will come apart in a "nuclear" explosion.

There is a lot more that can be said about the particles that make up atoms, perhaps someone else could go into greater detail.

Years ago, it was thought that the atom could not be divided. In fact According to the Merriam Webster dictionary, "the word "atom" comes from the Middle English, from Latin atomus, from Greek atomos, "indivisible". We have since learned that atoms are made of protons, neutrons, and electrons. Certain atoms can be split (fission) in nuclear reactors. In particular U235 and Pu239 are split in the atom bomb. Splitting atoms usually is accompanied by a large release of energy (the energy that bound the atoms together in the first place). The amount of energy is released depends on the atomic number and atomic mass of the atom.