The term dubiofossil is a portmanteau word used in geology and paleontology for a problematic structure that looks like a fossil but has an uncertain biologic origin.
Although ultimately such structures are either biogenic (i.e., fossil) or abiogenic (i.e., pseudofossil), the information available at the time of study is insufficient to make an unambiguous determination.
Physical and chemical processes can produce structures that look indistinguishable from some that are formed by biologic activity, presenting a hurdle in their interpretation.
Lines of evidence for biogenicity, called biosignatures, come in various forms and appear at various scales, ranging from the atomic to the planetary dimension.
Molecule-building, cell division, colony formation, respiration, excretion, active motility are amongst the biologic processes that effect changes in the environment and can leave distinctive morphologic features or signature chemical by-products in the geologic record.