3.2.5 Ascertaining whether there is a fallback position 

Claims sometimes contain an unclear and undefined term for which a clear preferred embodiment (i.e. a "fallback position"; see B‑III, 3.2(iv)) is given only in the description and/or drawings (see B‑III, 3.2.3). The search will then be based on the broadest technically sensible interpretation of the term. However, if the term's meaning is so unclear that a meaningful search cannot be carried out, it is justified to limit the scope of the search under Rule 63.