A lapsed Catholic is a baptized Catholic who is non-practicing. Such a person may still identify as a Catholic and remains a Catholic according to canon law.
The Merriam-Webster Dictionary definition of "lapsed" in relation to "lapsed Catholic" is "no longer believing or following the teachings of a religion". Lapsing is thus not necessarily connected with a lack of belief. However, Daniel Ford links being a lapsed Catholic with rejection of Catholic teaching, either totally or by being an "à la carte Catholic". Other sources associate the term with abandonment of practice of the Catholic religion rather than with rejection of its doctrine. Thus the Cambridge Advanced Learner's Dictionary defines "lapsed", again in relation to "lapsed Catholic", as "no longer involved in an activity or organization", and the Oxford Dictionary speaks only of "no longer following the rules and practices of a religion or doctrine".Richard John Neuhaus, quoting G.K. Chesterton's remark that a Protestant typically says he is a good Protestant, while a Catholic typically says he is a bad Catholic. For many, being a lapsed Catholic is just another way of being a Catholic.
According to Catholic belief, baptism "seals the Christian with the indelible spiritual mark of belonging to Christ. No sin can erase this mark, even if sin prevents baptism from bearing the fruits of salvation."
Even the form of censure known as excommunication does not in itself make a person an ex-Catholic: excommunicated persons are "cut off from the Church", barred from receiving the Eucharist and from taking an active part in the liturgy (reading, serving at the altar, etc.), but they remain Catholics. They are urged to retain a relationship with the Church, as the goal is to encourage them to repent and return to active participation in its life.
In the time of the persecution of Christians in the Roman Empire, many Christians, including clergy and even some bishops, failed to hold firm. They were referred to as the lapsi (those who had slipped and fell) as opposed to the stantes (those who stood firm). Different attitudes developed within the Church towards the lapsed: some held they should never be readmitted to the Church before death, others were for demanding serious penance of them before readmitting them, while others again were still more lenient. The First Council of Nicaea insisted that any clergy who had lapsed were not to be readmitted to clerical rank.