An "alarming" proportion of adults in Great Britain remain confused about what constitutes rape, campaigners say.
A third of people surveyed for the End Violence Against Women coalition said there had to be physical violence for sexual activity to count as rape.
A third of males and 21% of females said it would not usually be considered rape if a woman had flirted on a date.
EVAW said the responses of the 3,922 people surveyed shows that "myths about rape are still very common".
The law is unequivocal - rape is sex without consent - but many people appear unable to identify that certain behaviour amount to an offence, it added.
EVAW said younger respondents to the survey held views that are "more closely aligned to the law".
It said the vast majority of reports to police are about rape within relationships.
But pollsters for YouGov found more than a third of over-65s do not regard non-consensual sex in marriage or a relationship as rape, compared with 16% of people aged 16 to 24.
And 42% of over 65s said if sexual activity continues after a woman changes her mind it is not rape, compared with 22% of the 25-49s.
The survey, carried out online in September, also found:
- 6% of people say it is not rape if a woman is very drunk or asleep, with a further 5% saying they are unsure of the law on this
- Stealthing - removing a condom without a partner's consent - is not understood as rape, with 19% of people thinking this is never rape, and 21% think that this would not normally be rape
- 11% of respondents believe the more sexual partners a woman has, the less harm she will experience from a rape
Figures published in September in the Crown Prosecution Service's Violence Against Women And Girls report highlighted a 23.1% fall in the number of defendants charged with rape in England and Wales in 2017-2018, compared with the previous year, and a conviction rate of 36%.
Rachel Krys, EVAW co-director, added: "These figures are alarming because they show that a huge proportion of UK adults, who make up juries in rape trials, are still very unclear about what rape is.
"Confusion and myths about rape are still very common and this could explain why it's hard for juries to make fair decisions if they don't understand or agree with our laws on rape."
EVAW added the #MeToo campaign had shone the spotlight on sexual attacks and harassment by public figures - but also on the fact that people still have different understandings of what rape and sexual violence is.