A peplomer is a glycoprotein spike on a viral capsid or viral envelope. These protrusions will only bind to certain receptors on the host cell; they are essential for both host specificity and viral infectivity. The term 'peplomer' is typically used to refer to a grouping of heterologous proteins on the virus surface that function together.
The tail fibers of some bacteriophages, especially the T4-like phages, are modified peplomers. Influenza virus has two kinds of peplomers: 1) triangular, spike-shaped "haemagglutinin" and 2) mushroom-shaped "neuraminidase"
References
Peplomer Wikipedia(Text) CC BY-SA