Biologist/baɪˈɑːlədʒɪst/ Definition 1 of 2Pro Tip 1/3Field Specific Biologists specialize in various fields, so context determines their specific role. A marine biologist studies sea creatures. Pro Tip 2/3Research Focus A biologist usually does research, which can be fieldwork or lab work. The biologist spent months in the Amazon rainforest conducting research. Pro Tip 3/3Professional Title The title 'biologist' implies professional expertise, not just interest. After earning his Ph.D., he became a renowned biologist.