A road side memorial, usually in the form of a wreath or bunch of flowers Sellotaped to a lamp post or road sign to mark to place of a traffic accident in which fatalities occurred.
An amalgamation of the words 'Sellotape' and 'Cenotaph'. (Sellotape is a popular European brand name for sticky backed plastic tape, aka Scotch Tape.)
Maud - "Oh look Bernard, there's one of those Sellotaphs." (pointing at the flowers taped to a post on the side of the road)
Bernard - "Must have been an accident here." (looking at said flowers, taped to a post)
Maud - "Oh yes... In that case stop looking at the Sellotaph and keep your eyes on the road!" (Maud hits Bernard with hand bag)