The octal representation of the binary number $11011011$ is $333$.

To convert a binary number to its octal equivalent, we begin by grouping the binary digits into sets of three, starting from the right. If the total number of binary digits is not a multiple of three, we can add zeros to the left to complete the grouping. For the binary number $11011011$, we can group the digits as $011\ 011\ 011$.

Next, we convert each group of three binary digits into its corresponding octal digit. The binary group $011$ translates to the octal digit $3$. As a result, the octal representation of the binary number $11011011$ is $333$.

This conversion process is relatively straightforward because both octal and binary are base-2 systems. Each octal digit corresponds directly to exactly three binary digits, which simplifies the conversion. This characteristic contributed to the widespread use of octal in early computer systems. However, in contemporary computing, hexadecimal (base-16) has become more prevalent since it aligns more closely with the byte, the fundamental unit of information in modern computer architecture.