Fast mapping (FM) is a hypothetical, incidental learning process that allows rapid acquisition of new words. Using an implicit reaction time measure in a FM paradigm, Coutanche and Thompson‐Schill (2014) showed evidence of lexical competition within 10 minutes of nonwords being learned as names of unknown items, consistent with same‐day lexicalisation. Here, Experiment 1 was a methodological replication (N=28/group) that found no evidence of this RT competition effect. Instead, a post‐hoc analysis suggested evidence of semanticpriming. Experiment 2 (N=60/group, tested online, pre‐registered on OSF) tested whether semantic priming remained when making the stimulus set fully counterbalanced. No evidence for either lexical competition nor semantic priming was detected, and Bayes Factors for the combined data supported the hypothesis of no effect of lexical competition. These results, together with our previous work, question whether fast mapping exists in healthy adults, at least using this specific FM paradigm.