adj. Indifferent or blind to distress or hardship; uncaring.
Also Seen As
The image is shocking. For an hour, a little girl, clutching her doll, stands in a crowded shopping centre, clearly lost and appealing for help. But none of the adults stops. Hundreds ignore her until a kindly grandmother, who had already walked past, turns round and asks the seven-year-old if she is all right.

This is the scene to be witnessed on Little Girl Lost, a Channel Five documentary that purports to demonstrate how we have become a "walk-on-by" nation cowed by paedophile hysteria, suffocating criminal records checks and an irrational suspicion of all adult males
—Phillip Johnston, “Would you help a lost girl, or just walk on by?,” The Telegraph, March 24, 2014
Research by psychologists suggests Britain is very far from a "walk on by" culture.

Mark Levine, of Lancaster University, studied thousands of hours of CCTV footage of late night violence, and found that in the great majority of cases people do step in and try to defuse violent situations.
1996 (earliest)
John Sheppard was one of society's invisibles, an elderly, isolated man whose existence revolved around his small one-bedroom flat in North London. Sometime after his 69th birthday he died, as he had lived, quietly and alone, and it was three and a half years before two workmen, trying to trace a water leak, entered his flat and found his remains.

The case caused uproar, led to a rash of studies and inquiries that lambasted our hands-off, uncaring, walk-on-by society, and called for us all to be better neighbours.
—Kirsty Scott, “When we walk on by,” The Herald, January 12, 1996