An example of money laundering is depositing small portions of illegal cash into many different checking accounts of legal businesses and then writing checks from those account to obtain cash.
money laundering - Investment & Finance Definition
Making money that is generated through criminal activities appear as if it was earned through legitimate business activities. Detecting money-laundering activities is often very difficult because the money often is transferred between several accounts in order to conceal its true origins. As terrorism activities have increased, so too has the motivation for money laundering.