In freight terms, project cargo means the movement of goods that are too big or too wide for a standard container. Traditionally, project cargo dealt with moving heavy equipment for the oil and gas sector. Now, although still considered a niche market, project cargo has grown from strength to strength in this region, mainly because of the increased demand brought about by the diversity of projects.
But also you can define project cargo as,
The large, oversized, overweight heavy lift cargo or critical pieces of equipment that may be high value or time sensitive and sometimes both. Project cargo insurance covers against loss or damage in transit for critical components of large civil, production facility, infrastructure, and/or construction projects.