bit string

A bit array (or bitmap, in some cases) is an array data structure which compactly stores individual bits (boolean values). It implements a simple set data structure storing a subset of {1,2,...,n} and is effective at exploiting bit-level parallelism in hardware to perform operations quickly. A typical bit array stores kw bits, where w is the number of bits in the unit of storage, such as a byte or word, and k is some integer. If the number of bits to be stored does not divide w, some space is wasted due to internal fragmentation.
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A sequence of bits. Note: In a bit stream, individual bit strings may be separated by data delimiters.

<programming, data> An ordered sequence of bits. This is very similar to a bit pattern except that the term "string" suggests an arbitrary length sequence as opposed to a pre-determined length "pattern".